diff --git a/detectors/node/opentelemetry-resource-detector-aws/src/detectors/AwsEcsDetector.ts b/detectors/node/opentelemetry-resource-detector-aws/src/detectors/AwsEcsDetector.ts
index 45a5b74dab..6bd96ea9e8 100644
--- a/detectors/node/opentelemetry-resource-detector-aws/src/detectors/AwsEcsDetector.ts
+++ b/detectors/node/opentelemetry-resource-detector-aws/src/detectors/AwsEcsDetector.ts
@@ -163,10 +163,8 @@ export class AwsEcsDetector implements ResourceDetector {
       );
       const splitData = rawData.trim().split('\n');
       for (const str of splitData) {
-        if (str.length > AwsEcsDetector.CONTAINER_ID_LENGTH) {
-          containerId = str.substring(
-            str.length - AwsEcsDetector.CONTAINER_ID_LENGTH
-          );
+        containerId = this._extractContainerIdFromLine(str);
+        if (containerId) {
           break;
         }
       }
@@ -176,6 +174,74 @@ export class AwsEcsDetector implements ResourceDetector {
     return containerId;
   }
 
+  /**
+   * Extract container ID from a cgroup line.
+   * Handles the new AWS ECS Fargate format: /ecs/<taskId>/<taskId>-<containerId>
+   * Returns the last segment after the final '/' which should be the complete container ID.
+   */
+  private _extractContainerIdFromLine(line: string): string | undefined {
+    if (!line) {
+      return undefined;
+    }
+
+    // Split by '/' and get the last segment
+    const segments = line.split('/');
+    if (segments.length <= 1) {
+      // Fallback to original logic if no '/' found
+      if (line.length > AwsEcsDetector.CONTAINER_ID_LENGTH) {
+        return line.substring(line.length - AwsEcsDetector.CONTAINER_ID_LENGTH);
+      }
+      return undefined;
+    }
+
+    let lastSegment = segments[segments.length - 1];
+    
+    // Handle containerd v1.5.0+ format with systemd cgroup driver (e.g., ending with :cri-containerd:containerid)
+    const colonIndex = lastSegment.lastIndexOf(':');
+    if (colonIndex !== -1) {
+      lastSegment = lastSegment.substring(colonIndex + 1);
+    }
+
+    // Remove known prefixes if they exist
+    const prefixes = ['docker-', 'crio-', 'cri-containerd-'];
+    for (const prefix of prefixes) {
+      if (lastSegment.startsWith(prefix)) {
+        lastSegment = lastSegment.substring(prefix.length);
+        break;
+      }
+    }
+
+    // Remove anything after the first period (like .scope)
+    if (lastSegment.includes('.')) {
+      lastSegment = lastSegment.split('.')[0];
+    }
+
+    // Basic validation: should not be empty and should have reasonable length
+    if (!lastSegment || lastSegment.length < 8) {
+      return undefined;
+    }
+
+    // AWS ECS container IDs can be in various formats:
+    // 1. Pure hex strings: 'abcdef123456'
+    // 2. ECS format: 'taskId-containerId' 
+    // 3. Mixed alphanumeric with hyphens
+    // We'll be more permissive and allow alphanumeric characters and hyphens
+    const containerIdPattern = /^[a-zA-Z0-9\-_]+$/;
+    
+    if (containerIdPattern.test(lastSegment)) {
+      return lastSegment;
+    }
+
+    // If the pattern doesn't match but the segment looks reasonable,
+    // still try to return it (last resort for edge cases)
+    if (lastSegment.length >= 12 && lastSegment.length <= 128) {
+      diag.debug(`AwsEcsDetector: Using container ID with non-standard format: ${lastSegment}`);
+      return lastSegment;
+    }
+
+    return undefined;
+  }
+
   /**
    * Add metadata-v4-related resource attributes to `data` (in-place)
    */
diff --git a/detectors/node/opentelemetry-resource-detector-aws/test/detectors/AwsEcsDetector.test.ts b/detectors/node/opentelemetry-resource-detector-aws/test/detectors/AwsEcsDetector.test.ts
index 1258de46a6..7c171c093a 100644
--- a/detectors/node/opentelemetry-resource-detector-aws/test/detectors/AwsEcsDetector.test.ts
+++ b/detectors/node/opentelemetry-resource-detector-aws/test/detectors/AwsEcsDetector.test.ts
@@ -453,3 +453,291 @@ describe('AwsEcsResourceDetector', () => {
     });
   });
 });
+
+describe('AwsEcsDetector - Container ID extraction improvements', () => {
+  let readStub: sinon.SinonStub;
+
+  beforeEach(() => {
+    process.env.ECS_CONTAINER_METADATA_URI_V4 = 'http://169.254.170.2/v4/test';
+  });
+
+  afterEach(() => {
+    sinon.restore();
+  });
+
+  describe('New AWS ECS Fargate cgroup format support', () => {
+    it('should extract full container ID from new AWS ECS Fargate format', async () => {
+      const taskId = 'c23e5f76c09d438aa1824ca4058bdcab';
+      const containerId = '1234567890abcdef';
+      const cgroupData = `/ecs/${taskId}/${taskId}-${containerId}`;
+      
+      sinon.stub(os, 'hostname').returns('test-hostname');
+      readStub = sinon
+        .stub(AwsEcsDetector, 'readFileAsync' as any)
+        .resolves(cgroupData);
+      
+      // Mock the metadata requests
+      const nockScope = nock('http://169.254.170.2:80')
+        .persist(false)
+        .get('/v4/test')
+        .reply(200, { ContainerARN: 'arn:aws:ecs:us-west-2:111122223333:container/test' })
+        .get('/v4/test/task')
+        .reply(200, { 
+          TaskARN: 'arn:aws:ecs:us-west-2:111122223333:task/default/test',
+          Family: 'test-family',
+          Revision: '1',
+          Cluster: 'test-cluster',
+          LaunchType: 'FARGATE'
+        });
+
+      const resource = detectResources({ detectors: [awsEcsDetector] });
+      await resource.waitForAsyncAttributes?.();
+
+      sinon.assert.calledOnce(readStub);
+      assert.ok(resource);
+      assertEcsResource(resource, {});
+      assertContainerResource(resource, {
+        name: 'test-hostname',
+        id: `${taskId}-${containerId}`, // Expected: full taskId-containerId, not truncated
+      });
+      
+      nockScope.done();
+    });
+
+    it('should extract container ID from long cgroup path without truncation', async () => {
+      // Simulate the actual issue where the path is longer than 64 chars
+      const longTaskId = 'abcdefgh12345678abcdefgh12345678abcdefgh12345678';
+      const containerId = '1234567890abcdef';
+      const cgroupData = `/ecs/${longTaskId}/${longTaskId}-${containerId}`;
+      
+      sinon.stub(os, 'hostname').returns('test-hostname');
+      readStub = sinon
+        .stub(AwsEcsDetector, 'readFileAsync' as any)
+        .resolves(cgroupData);
+      
+      // Mock the metadata requests  
+      const nockScope = nock('http://169.254.170.2:80')
+        .persist(false)
+        .get('/v4/test')
+        .reply(200, { ContainerARN: 'arn:aws:ecs:us-west-2:111122223333:container/test' })
+        .get('/v4/test/task')
+        .reply(200, { 
+          TaskARN: 'arn:aws:ecs:us-west-2:111122223333:task/default/test',
+          Family: 'test-family',
+          Revision: '1',
+          Cluster: 'test-cluster',
+          LaunchType: 'FARGATE'
+        });
+
+      const resource = detectResources({ detectors: [awsEcsDetector] });
+      await resource.waitForAsyncAttributes?.();
+
+      sinon.assert.calledOnce(readStub);
+      assert.ok(resource);
+      assertEcsResource(resource, {});
+      assertContainerResource(resource, {
+        name: 'test-hostname',
+        id: `${longTaskId}-${containerId}`, // Should get full ID, not truncated
+      });
+      
+      nockScope.done();
+    });
+
+    it('should handle multiple cgroup lines and pick the valid one', async () => {
+      const taskId = 'c23e5f76c09d438aa1824ca4058bdcab';
+      const containerId = '1234567890abcdef';
+      const cgroupData = [
+        '12:memory:/ecs',
+        '11:cpu:/ecs/task-id',
+        `10:devices:/ecs/${taskId}/${taskId}-${containerId}`,
+        '9:freezer:/ecs'
+      ].join('\n');
+      
+      sinon.stub(os, 'hostname').returns('test-hostname');
+      readStub = sinon
+        .stub(AwsEcsDetector, 'readFileAsync' as any)
+        .resolves(cgroupData);
+      
+      // Mock the metadata requests
+      const nockScope = nock('http://169.254.170.2:80')
+        .persist(false)
+        .get('/v4/test')
+        .reply(200, { ContainerARN: 'arn:aws:ecs:us-west-2:111122223333:container/test' })
+        .get('/v4/test/task')
+        .reply(200, { 
+          TaskARN: 'arn:aws:ecs:us-west-2:111122223333:task/default/test',
+          Family: 'test-family',
+          Revision: '1',
+          Cluster: 'test-cluster',
+          LaunchType: 'FARGATE'
+        });
+
+      const resource = detectResources({ detectors: [awsEcsDetector] });
+      await resource.waitForAsyncAttributes?.();
+
+      sinon.assert.calledOnce(readStub);
+      assert.ok(resource);
+      assertEcsResource(resource, {});
+      assertContainerResource(resource, {
+        name: 'test-hostname',
+        id: `${taskId}-${containerId}`,
+      });
+      
+      nockScope.done();
+    });
+  });
+
+  describe('Edge cases and format variations', () => {
+    it('should handle containerd format with colon separators', async () => {
+      const taskId = 'c23e5f76c09d438aa1824ca4058bdcab';
+      const containerId = '1234567890abcdef';
+      const cgroupData = `0::/system.slice/containerd.service/kubepods-burstable-pod.slice:cri-containerd:${taskId}-${containerId}`;
+      
+      sinon.stub(os, 'hostname').returns('test-hostname');
+      readStub = sinon
+        .stub(AwsEcsDetector, 'readFileAsync' as any)
+        .resolves(cgroupData);
+      
+      // Mock the metadata requests
+      const nockScope = nock('http://169.254.170.2:80')
+        .persist(false)
+        .get('/v4/test')
+        .reply(200, { ContainerARN: 'arn:aws:ecs:us-west-2:111122223333:container/test' })
+        .get('/v4/test/task')
+        .reply(200, { 
+          TaskARN: 'arn:aws:ecs:us-west-2:111122223333:task/default/test',
+          Family: 'test-family',
+          Revision: '1',
+          Cluster: 'test-cluster',
+          LaunchType: 'FARGATE'
+        });
+
+      const resource = detectResources({ detectors: [awsEcsDetector] });
+      await resource.waitForAsyncAttributes?.();
+
+      sinon.assert.calledOnce(readStub);
+      assert.ok(resource);
+      assertEcsResource(resource, {});
+      assertContainerResource(resource, {
+        name: 'test-hostname',
+        id: `${taskId}-${containerId}`,
+      });
+      
+      nockScope.done();
+    });
+
+    it('should handle docker prefix and scope suffix', async () => {
+      const taskId = 'c23e5f76c09d438aa1824ca4058bdcab';
+      const containerId = '1234567890abcdef';
+      const cgroupData = `/docker/docker-${taskId}-${containerId}.scope`;
+      
+      sinon.stub(os, 'hostname').returns('test-hostname');
+      readStub = sinon
+        .stub(AwsEcsDetector, 'readFileAsync' as any)
+        .resolves(cgroupData);
+      
+      // Mock the metadata requests
+      const nockScope = nock('http://169.254.170.2:80')
+        .persist(false)
+        .get('/v4/test')
+        .reply(200, { ContainerARN: 'arn:aws:ecs:us-west-2:111122223333:container/test' })
+        .get('/v4/test/task')
+        .reply(200, { 
+          TaskARN: 'arn:aws:ecs:us-west-2:111122223333:task/default/test',
+          Family: 'test-family',
+          Revision: '1',
+          Cluster: 'test-cluster',
+          LaunchType: 'FARGATE'
+        });
+
+      const resource = detectResources({ detectors: [awsEcsDetector] });
+      await resource.waitForAsyncAttributes?.();
+
+      sinon.assert.calledOnce(readStub);
+      assert.ok(resource);
+      assertEcsResource(resource, {});
+      assertContainerResource(resource, {
+        name: 'test-hostname',
+        id: `${taskId}-${containerId}`,
+      });
+      
+      nockScope.done();
+    });
+
+    it('should return undefined for invalid container ID formats', async () => {
+      const invalidCgroupData = '/invalid/path/with/non-hex-characters!!!';
+      
+      sinon.stub(os, 'hostname').returns('test-hostname');
+      readStub = sinon
+        .stub(AwsEcsDetector, 'readFileAsync' as any)
+        .resolves(invalidCgroupData);
+      
+      // Mock the metadata requests
+      const nockScope = nock('http://169.254.170.2:80')
+        .persist(false)
+        .get('/v4/test')
+        .reply(200, { ContainerARN: 'arn:aws:ecs:us-west-2:111122223333:container/test' })
+        .get('/v4/test/task')
+        .reply(200, { 
+          TaskARN: 'arn:aws:ecs:us-west-2:111122223333:task/default/test',
+          Family: 'test-family',
+          Revision: '1',
+          Cluster: 'test-cluster',
+          LaunchType: 'FARGATE'
+        });
+
+      const resource = detectResources({ detectors: [awsEcsDetector] });
+      await resource.waitForAsyncAttributes?.();
+
+      sinon.assert.calledOnce(readStub);
+      assert.ok(resource);
+      assertEcsResource(resource, {});
+      assertContainerResource(resource, {
+        name: 'test-hostname',
+        // id should be undefined due to invalid format
+      });
+      
+      nockScope.done();
+    });
+  });
+
+  describe('Backward compatibility', () => {
+    it('should fallback to original logic for legacy format', async () => {
+      // Test backward compatibility with existing 64-char format
+      const legacyContainerId = 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklm';
+      
+      sinon.stub(os, 'hostname').returns('test-hostname');
+      readStub = sinon
+        .stub(AwsEcsDetector, 'readFileAsync' as any)
+        .resolves(legacyContainerId);
+      
+      // Mock the metadata requests
+      const nockScope = nock('http://169.254.170.2:80')
+        .persist(false)
+        .get('/v4/test')
+        .reply(200, { ContainerARN: 'arn:aws:ecs:us-west-2:111122223333:container/test' })
+        .get('/v4/test/task')
+        .reply(200, { 
+          TaskARN: 'arn:aws:ecs:us-west-2:111122223333:task/default/test',
+          Family: 'test-family',
+          Revision: '1',
+          Cluster: 'test-cluster',
+          LaunchType: 'FARGATE'
+        });
+
+      const resource = detectResources({ detectors: [awsEcsDetector] });
+      await resource.waitForAsyncAttributes?.();
+
+      sinon.assert.calledOnce(readStub);
+      assert.ok(resource);
+      assertEcsResource(resource, {});
+      assertContainerResource(resource, {
+        name: 'test-hostname',
+        id: 'bcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklm', // Last 64 chars
+      });
+      
+      nockScope.done();
+    });
+  });
+});
+