diff --git a/dist/index.js b/dist/index.js
index a0e90b7..ae5047a 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -16001,6 +16001,27 @@ async function fetch_changed_files() {
   return changed_files;
 }
 
+async function fetch_current_reviewers() {
+  const context = get_context();
+  const octokit = get_octokit();
+
+  const current_reviewers = [];
+
+  // API docs
+  // Generated octokit methods: https://github.com/octokit/plugin-rest-endpoint-methods.js/blob/main/src/generated/endpoints.ts
+  // Available Rest APIs: https://docs.github.com/en/rest/pulls/review-requests?apiVersion=2022-11-28#get-all-requested-reviewers-for-a-pull-request
+  const { data: response_body } = await octokit.pulls.listRequestedReviewers({
+    owner: context.repo.owner,
+    repo: context.repo.repo,
+    pull_number: context.payload.pull_request.number,
+  });
+
+  current_reviewers.push(...response_body.users.map((user) => user.login));
+  current_reviewers.push(...response_body.teams.map((team) => 'team:'.concat(team.slug)));
+
+  return current_reviewers;
+}
+
 async function assign_reviewers(reviewers) {
   const context = get_context();
   const octokit = get_octokit();
@@ -16061,6 +16082,7 @@ module.exports = {
   get_pull_request,
   fetch_config,
   fetch_changed_files,
+  fetch_current_reviewers,
   assign_reviewers,
   clear_cache,
 };
@@ -16118,6 +16140,10 @@ async function run() {
   core.info('Fetching changed files in the pull request');
   const changed_files = await github.fetch_changed_files();
 
+  core.info('Fetching currently requested reviewers');
+  const current_reviewers = await github.fetch_current_reviewers();
+  core.info(`Already in review: ${current_reviewers.join(', ')}`);
+
   core.info('Identifying reviewers based on the changed files');
   const reviewers_based_on_files = identify_reviewers_by_changed_files({ config, changed_files, excludes: [ author ] });
 
@@ -16142,11 +16168,18 @@ async function run() {
     reviewers.push(...default_reviewers);
   }
 
+  core.info(`Possible Reviewers ${reviewers.join(', ')}, prepare filtering out already requested reviewers`);
+  reviewers = reviewers.filter((reviewer) => !current_reviewers.includes(reviewer));
+
   core.info('Randomly picking reviewers if the number of reviewers is set');
   reviewers = randomly_pick_reviewers({ reviewers, config });
 
-  core.info(`Requesting review to ${reviewers.join(', ')}`);
-  await github.assign_reviewers(reviewers);
+  if (reviewers.length > 0) {
+    core.info(`Requesting review to ${reviewers.join(', ')}`);
+    await github.assign_reviewers(reviewers);
+  } else {
+    core.info('No new reviewers to assign to PR');
+  }
 }
 
 module.exports = {
diff --git a/src/github.js b/src/github.js
index 11ff8ad..b02ae4c 100644
--- a/src/github.js
+++ b/src/github.js
@@ -96,6 +96,27 @@ async function fetch_changed_files() {
   return changed_files;
 }
 
+async function fetch_current_reviewers() {
+  const context = get_context();
+  const octokit = get_octokit();
+
+  const current_reviewers = [];
+
+  // API docs
+  // Generated octokit methods: https://github.com/octokit/plugin-rest-endpoint-methods.js/blob/main/src/generated/endpoints.ts
+  // Available Rest APIs: https://docs.github.com/en/rest/pulls/review-requests?apiVersion=2022-11-28#get-all-requested-reviewers-for-a-pull-request
+  const { data: response_body } = await octokit.pulls.listRequestedReviewers({
+    owner: context.repo.owner,
+    repo: context.repo.repo,
+    pull_number: context.payload.pull_request.number,
+  });
+
+  current_reviewers.push(...response_body.users.map((user) => user.login));
+  current_reviewers.push(...response_body.teams.map((team) => 'team:'.concat(team.slug)));
+
+  return current_reviewers;
+}
+
 async function assign_reviewers(reviewers) {
   const context = get_context();
   const octokit = get_octokit();
@@ -156,6 +177,7 @@ module.exports = {
   get_pull_request,
   fetch_config,
   fetch_changed_files,
+  fetch_current_reviewers,
   assign_reviewers,
   clear_cache,
 };
diff --git a/src/index.js b/src/index.js
index 5d23032..1207a47 100644
--- a/src/index.js
+++ b/src/index.js
@@ -44,6 +44,10 @@ async function run() {
   core.info('Fetching changed files in the pull request');
   const changed_files = await github.fetch_changed_files();
 
+  core.info('Fetching currently requested reviewers');
+  const current_reviewers = await github.fetch_current_reviewers();
+  core.info(`Already in review: ${current_reviewers.join(', ')}`);
+
   core.info('Identifying reviewers based on the changed files');
   const reviewers_based_on_files = identify_reviewers_by_changed_files({ config, changed_files, excludes: [ author ] });
 
@@ -68,11 +72,18 @@ async function run() {
     reviewers.push(...default_reviewers);
   }
 
+  core.info(`Possible Reviewers ${reviewers.join(', ')}, prepare filtering out already requested reviewers`);
+  reviewers = reviewers.filter((reviewer) => !current_reviewers.includes(reviewer));
+
   core.info('Randomly picking reviewers if the number of reviewers is set');
   reviewers = randomly_pick_reviewers({ reviewers, config });
 
-  core.info(`Requesting review to ${reviewers.join(', ')}`);
-  await github.assign_reviewers(reviewers);
+  if (reviewers.length > 0) {
+    core.info(`Requesting review to ${reviewers.join(', ')}`);
+    await github.assign_reviewers(reviewers);
+  } else {
+    core.info('No new reviewers to assign to PR');
+  }
 }
 
 module.exports = {
diff --git a/test/github.test.js b/test/github.test.js
index 7a21ca5..a65c194 100644
--- a/test/github.test.js
+++ b/test/github.test.js
@@ -12,6 +12,7 @@ const {
   get_pull_request,
   fetch_config,
   fetch_changed_files,
+  fetch_current_reviewers,
   assign_reviewers,
   clear_cache,
 } = require('../src/github');
@@ -123,6 +124,66 @@ describe('github', function() {
     });
   });
 
+  describe('fetch_current_reviewers()', function() {
+    const stub = sinon.stub();
+    const octokit = {
+      pulls: {
+        listRequestedReviewers: stub,
+      },
+    };
+
+    beforeEach(function() {
+      github.getOctokit.returns(octokit);
+    });
+
+    it('fetches current reviewers - user only', async function() {
+      stub.returns({
+        data: {
+          users: [
+            { login: 'super/mario/64' },
+          ],
+          teams: [],
+        },
+      });
+      const expected = [ 'super/mario/64' ];
+      const actual = await fetch_current_reviewers();
+      expect(actual).to.deep.equal(expected);
+    });
+
+    it('fetches current reviewers - team only', async function() {
+      stub.returns({
+        data: {
+          users: [ ],
+          teams: [
+            { slug: 'super_marios' },
+          ],
+        },
+      });
+      const expected = [ 'team:super_marios' ];
+      const actual = await fetch_current_reviewers();
+      expect(actual).to.deep.equal(expected);
+    });
+
+    it('fetches current reviewers - combined users and teams', async function() {
+      stub.returns({
+        data: {
+          users: [
+            { login: 'bowser' },
+            { login: 'peach' },
+            { login: 'luigi' },
+          ],
+          teams: [
+            { slug: 'super_marios' },
+            { slug: 'toads' },
+          ],
+        },
+      });
+      const expected = [ 'bowser', 'peach', 'luigi', 'team:super_marios', 'team:toads' ];
+      const actual = await fetch_current_reviewers();
+      expect(actual).to.deep.equal(expected);
+    });
+  });
+
   describe('assign_reviewers()', function() {
     const spy = sinon.spy();
     const octokit = {
diff --git a/test/index.test.js b/test/index.test.js
index 4bbfe21..a9d8db4 100644
--- a/test/index.test.js
+++ b/test/index.test.js
@@ -14,6 +14,7 @@ describe('index', function() {
       sinon.stub(github, 'get_pull_request');
       sinon.stub(github, 'fetch_config');
       sinon.stub(github, 'fetch_changed_files');
+      sinon.stub(github, 'fetch_current_reviewers');
       sinon.stub(github, 'assign_reviewers');
     });
 
@@ -21,6 +22,7 @@ describe('index', function() {
       github.get_pull_request.restore();
       github.fetch_config.restore();
       github.fetch_changed_files.restore();
+      github.fetch_current_reviewers.restore();
       github.assign_reviewers.restore();
     });
 
@@ -49,12 +51,116 @@ describe('index', function() {
       const changed_fiels = [ 'path/to/file.js' ];
       github.fetch_changed_files.returns(changed_fiels);
 
+      const current_reviewers = [];
+      github.fetch_current_reviewers.returns(current_reviewers);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.true;
       expect(github.assign_reviewers.lastCall.args[0]).to.have.members([ 'mario', 'princess-peach' ]);
     });
 
+    it('skips single alias if already a reviewer', async function() {
+      const config = {
+        reviewers: {
+          defaults: [ 'dr-mario' ],
+          groups: {
+            'mario-brothers': [ 'mario', 'luigi' ],
+          },
+        },
+        files: {
+          '**/*.js': [ 'mario-brothers', 'princess-peach' ],
+          '**/*.rb': [ 'wario', 'waluigi' ],
+        },
+      };
+      github.fetch_config.returns(config);
+
+      const pull_request = {
+        title: 'Nice Pull Request',
+        is_draft: false,
+        author: 'luigi',
+      };
+      github.get_pull_request.returns(pull_request);
+
+      const changed_files = [ 'path/to/file.js' ];
+      github.fetch_changed_files.returns(changed_files);
+
+      const current_reviewers = [ 'princess-peach' ];
+      github.fetch_current_reviewers.returns(current_reviewers);
+
+      await run();
+
+      expect(github.assign_reviewers.calledOnce).to.be.true;
+      expect(github.assign_reviewers.lastCall.args[0]).to.have.members([ 'mario' ]);
+    });
+
+    it('skips team alias if already a reviewer', async function() {
+      const config = {
+        reviewers: {
+          defaults: [ 'dr-mario' ],
+          groups: {
+            'mario-brothers': [ 'mario', 'luigi' ],
+          },
+        },
+        files: {
+          '**/*.js': [ 'mario-brothers', 'team:peach-alliance' ],
+          '**/*.rb': [ 'wario', 'waluigi', 'team:bowser-and-co' ],
+        },
+      };
+      github.fetch_config.returns(config);
+
+      const pull_request = {
+        title: 'Nice Pull Request',
+        is_draft: false,
+        author: 'luigi',
+      };
+      github.get_pull_request.returns(pull_request);
+
+      const changed_files = [ 'path/to/file.js', 'path/to/file.rb' ];
+      github.fetch_changed_files.returns(changed_files);
+
+      const current_reviewers = [ 'team:bowser-and-co' ];
+      github.fetch_current_reviewers.returns(current_reviewers);
+
+      await run();
+
+      expect(github.assign_reviewers.calledOnce).to.be.true;
+      expect(github.assign_reviewers.lastCall.args[0]).to.have.members([ 'mario', 'team:peach-alliance', 'wario', 'waluigi' ]);
+    });
+
+    it('skips caling assign if no reviewers', async function() {
+      const config = {
+        reviewers: {
+          defaults: [ 'dr-mario' ],
+          groups: {
+            'mario-brothers': [ 'mario', 'luigi' ],
+          },
+        },
+        files: {
+          '**/*.js': [ 'mario-brothers', 'princess-peach' ],
+          '**/*.rb': [ 'wario', 'waluigi' ],
+        },
+      };
+      github.fetch_config.returns(config);
+
+      const pull_request = {
+        title: 'Nice Pull Request',
+        is_draft: false,
+        author: 'luigi',
+      };
+      github.get_pull_request.returns(pull_request);
+
+      const changed_files = [ 'path/to/file.js' ];
+      github.fetch_changed_files.returns(changed_files);
+
+      const current_reviewers = [ 'princess-peach', 'mario' ];
+      github.fetch_current_reviewers.returns(current_reviewers);
+
+      await run();
+
+      expect(github.assign_reviewers.calledOnce).to.be.false;
+    });
+
     it('requests review based on groups that author belongs to', async function() {
       const config = {
         reviewers: {
@@ -80,6 +186,9 @@ describe('index', function() {
       const changed_fiels = [];
       github.fetch_changed_files.returns(changed_fiels);
 
+      const current_reviewers = [];
+      github.fetch_current_reviewers.returns(current_reviewers);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.true;
@@ -107,6 +216,9 @@ describe('index', function() {
       const changed_fiels = [ 'path/to/file.js' ];
       github.fetch_changed_files.returns(changed_fiels);
 
+      const current_reviewers = [];
+      github.fetch_current_reviewers.returns(current_reviewers);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.false;
@@ -133,6 +245,9 @@ describe('index', function() {
       const changed_fiels = [ 'path/to/file.js' ];
       github.fetch_changed_files.returns(changed_fiels);
 
+      const current_reviewers = [];
+      github.fetch_current_reviewers.returns(current_reviewers);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.false;
@@ -162,6 +277,9 @@ describe('index', function() {
       const changed_fiels = [ 'path/to/file.py' ];
       github.fetch_changed_files.returns(changed_fiels);
 
+      const current_reviewers = [];
+      github.fetch_current_reviewers.returns(current_reviewers);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.false;
@@ -192,6 +310,9 @@ describe('index', function() {
       const changed_fiels = [ 'path/to/file.py' ];
       github.fetch_changed_files.returns(changed_fiels);
 
+      const current_reviewers = [];
+      github.fetch_current_reviewers.returns(current_reviewers);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.true;
@@ -223,6 +344,9 @@ describe('index', function() {
       const changed_fiels = [];
       github.fetch_changed_files.returns(changed_fiels);
 
+      const current_reviewers = [];
+      github.fetch_current_reviewers.returns(current_reviewers);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.true;
@@ -254,6 +378,9 @@ describe('index', function() {
       const changed_fiels = [];
       github.fetch_changed_files.returns(changed_fiels);
 
+      const current_reviewers = [];
+      github.fetch_current_reviewers.returns(current_reviewers);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.true;
@@ -283,6 +410,9 @@ describe('index', function() {
       const changed_fiels = [];
       github.fetch_changed_files.returns(changed_fiels);
 
+      const current_reviewers = [];
+      github.fetch_current_reviewers.returns(current_reviewers);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.true;