diff --git a/modules/dasBidAdapter.js b/modules/dasBidAdapter.js
index a01aaa96149..45e3ce88942 100644
--- a/modules/dasBidAdapter.js
+++ b/modules/dasBidAdapter.js
@@ -164,6 +164,17 @@ function buildUserIds(customParams) {
   return userIds;
 }
 
+function buildUserEids(bidRequests) {
+  const eids = deepAccess(bidRequests, '0.userIdAsEids');
+  if (!Array.isArray(eids) || eids.length === 0) {
+    return null;
+  }
+
+  const onetEids = eids.filter(eid => eid.source === 'onet.pl');
+
+  return onetEids.length > 0 ? onetEids : null;
+}
+
 function getNpaFromPubConsent(pubConsent) {
   const params = new URLSearchParams(pubConsent);
   return params.get('npa') === '1';
@@ -259,6 +270,12 @@ function buildOpenRTBRequest(bidRequests, bidderRequest) {
     }
   }
 
+  const userEids = buildUserEids(bidRequests);
+
+  if (userEids) {
+    request.user.eids = userEids;
+  }
+
   return request;
 }
 
diff --git a/test/spec/modules/dasBidAdapter_spec.js b/test/spec/modules/dasBidAdapter_spec.js
index d38592e47c4..271a1afb9f0 100644
--- a/test/spec/modules/dasBidAdapter_spec.js
+++ b/test/spec/modules/dasBidAdapter_spec.js
@@ -575,5 +575,59 @@ describe('dasBidAdapter', function () {
       const bidResponses = spec.interpretResponse(nativeResponse);
       expect(bidResponses[0].native).to.deep.equal({});
     });
+
+    describe('user.eids from userIdAsEids', function () {
+      const onetEid = {
+        source: 'onet.pl',
+        inserter: 'onet.pl',
+        uids: [{ id: 'test-artemis-id', atype: 1, ext: { id_type: 'tracking', consent_required: true } }]
+      };
+
+      it('should include user.eids when onet.pl EID is present in userIdAsEids', function () {
+        const bidRequestsWithEids = [{
+          ...bidRequests[0],
+          userIdAsEids: [onetEid]
+        }];
+
+        const request = spec.buildRequests(bidRequestsWithEids, bidderRequest);
+        const payload = JSON.parse(decodeURIComponent(new URL(request.url).searchParams.get('data')));
+
+        expect(payload.user.eids).to.be.an('array').with.lengthOf(1);
+        expect(payload.user.eids[0].source).to.equal('onet.pl');
+        expect(payload.user.eids[0].inserter).to.equal('onet.pl');
+        expect(payload.user.eids[0].uids[0].id).to.equal('test-artemis-id');
+        expect(payload.user.eids[0].uids[0].atype).to.equal(1);
+        expect(payload.user.eids[0].uids[0].ext.id_type).to.equal('tracking');
+        expect(payload.user.eids[0].uids[0].ext.consent_required).to.equal(true);
+      });
+
+      it('should not include user.eids when userIdAsEids is absent', function () {
+        const request = spec.buildRequests(bidRequests, bidderRequest);
+        const payload = JSON.parse(decodeURIComponent(new URL(request.url).searchParams.get('data')));
+
+        expect(payload.user).to.not.have.property('eids');
+      });
+
+      it('should not include user.eids when userIdAsEids contains no onet.pl source', function () {
+        const bidRequestsWithOtherEid = [{
+          ...bidRequests[0],
+          userIdAsEids: [{ source: 'other-source.com', uids: [{ id: 'some-id', atype: 1 }] }]
+        }];
+
+        const request = spec.buildRequests(bidRequestsWithOtherEid, bidderRequest);
+        const payload = JSON.parse(decodeURIComponent(new URL(request.url).searchParams.get('data')));
+
+        expect(payload.user).to.not.have.property('eids');
+      });
+
+      it('should not include user.eids when userIdAsEids is empty', function () {
+        const bidRequestsWithEmptyEids = [{ ...bidRequests[0], userIdAsEids: [] }];
+
+        const request = spec.buildRequests(bidRequestsWithEmptyEids, bidderRequest);
+        const payload = JSON.parse(decodeURIComponent(new URL(request.url).searchParams.get('data')));
+
+        expect(payload.user).to.not.have.property('eids');
+      });
+    });
   });
 });