diff --git a/pkg/reconciler/pipelinerun/affinity_assistant.go b/pkg/reconciler/pipelinerun/affinity_assistant.go
index baf31da6eb5..e97f89a83ee 100644
--- a/pkg/reconciler/pipelinerun/affinity_assistant.go
+++ b/pkg/reconciler/pipelinerun/affinity_assistant.go
@@ -139,6 +139,11 @@ func affinityAssistantStatefulSet(name string, pr *v1beta1.PipelineRun, claimNam
 		nodeSelector = pr.Spec.PodTemplate.NodeSelector
 	}
 
+	serviceAccount := "default"
+	if pr.Spec.ServiceAccountName != "" {
+		serviceAccount = pr.Spec.ServiceAccountName
+	}
+
 	containers := []corev1.Container{{
 		Name:  "affinity-assistant",
 		Image: affinityAssistantImage,
@@ -192,9 +197,10 @@ func affinityAssistantStatefulSet(name string, pr *v1beta1.PipelineRun, claimNam
 					Labels: getStatefulSetLabels(pr, name),
 				},
 				Spec: corev1.PodSpec{
-					Containers:   containers,
-					Tolerations:  tolerations,
-					NodeSelector: nodeSelector,
+					Containers:         containers,
+					Tolerations:        tolerations,
+					NodeSelector:       nodeSelector,
+					ServiceAccountName: serviceAccount,
 					Affinity: &corev1.Affinity{
 						PodAntiAffinity: &corev1.PodAntiAffinity{
 							PreferredDuringSchedulingIgnoredDuringExecution: []corev1.WeightedPodAffinityTerm{repelOtherAffinityAssistantsPodAffinityTerm},
diff --git a/pkg/reconciler/pipelinerun/affinity_assistant_test.go b/pkg/reconciler/pipelinerun/affinity_assistant_test.go
index c943290f490..b0bd4401b3d 100644
--- a/pkg/reconciler/pipelinerun/affinity_assistant_test.go
+++ b/pkg/reconciler/pipelinerun/affinity_assistant_test.go
@@ -117,6 +117,24 @@ func TestThatCustomTolerationsAndNodeSelectorArePropagatedToAffinityAssistant(t
 	}
 }
 
+func TestThatCustomServiceAccountIsPropagatedToAffinityAssistant(t *testing.T) {
+	prWithCustomPodTemplate := &v1beta1.PipelineRun{
+		TypeMeta: metav1.TypeMeta{Kind: "PipelineRun"},
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "pipelinerun-with-custom-podtemplate",
+		},
+		Spec: v1beta1.PipelineRunSpec{
+			ServiceAccountName: "test-service-account",
+			PodTemplate:        &pod.Template{},
+		},
+	}
+
+	stsWithServiceAccount := affinityAssistantStatefulSet("test-assistant", prWithCustomPodTemplate, "mypvc", "nginx")
+	if stsWithServiceAccount.Spec.Template.Spec.ServiceAccountName != "test-service-account" {
+		t.Errorf("expected non-default ServiceAccountName in the StatefulSet")
+	}
+}
+
 func TestThatTheAffinityAssistantIsWithoutNodeSelectorAndTolerations(t *testing.T) {
 	prWithoutCustomPodTemplate := &v1beta1.PipelineRun{
 		TypeMeta: metav1.TypeMeta{Kind: "PipelineRun"},