diff --git a/CHANGELOG.md b/CHANGELOG.md
index aac70563f19..1ea59aee1dc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,2 +1,3 @@
+- Fixed an issue where the functions service account option was not treated as a param (#6389).
 - Fixed an issue with deploying function groups containing v2 functions. (#6408)
 - Use GetDefaultBucket endpoint to fetch Storage Default Bucket.
diff --git a/src/deploy/functions/build.ts b/src/deploy/functions/build.ts
index 846a49043b3..573a199ab4e 100644
--- a/src/deploy/functions/build.ts
+++ b/src/deploy/functions/build.ts
@@ -235,7 +235,7 @@ export type Endpoint = Triggered & {
   // The services account that this function should run as.
   // defaults to the GAE service account when a function is first created as a GCF gen 1 function.
   // Defaults to the compute service account when a function is first created as a GCF gen 2 function.
-  serviceAccount?: ServiceAccount | null;
+  serviceAccount?: Field<string> | ServiceAccount | null;
 
   // defaults to ["us-central1"], overridable in firebase-tools with
   //  process.env.FIREBASE_FUNCTIONS_DEFAULT_REGION
@@ -457,8 +457,7 @@ export function toBackend(
         bdEndpoint,
         "environmentVariables",
         "labels",
-        "secretEnvironmentVariables",
-        "serviceAccount"
+        "secretEnvironmentVariables"
       );
 
       proto.convertIfPresent(bkEndpoint, bdEndpoint, "ingressSettings", (from) => {
@@ -479,6 +478,7 @@ export function toBackend(
         return (mem as backend.MemoryOptions) || null;
       });
 
+      r.resolveStrings(bkEndpoint, bdEndpoint, "serviceAccount");
       r.resolveInts(
         bkEndpoint,
         bdEndpoint,
diff --git a/src/test/deploy/functions/build.spec.ts b/src/test/deploy/functions/build.spec.ts
index 873c9a2a3b7..0f29dd55f08 100644
--- a/src/test/deploy/functions/build.spec.ts
+++ b/src/test/deploy/functions/build.spec.ts
@@ -1,5 +1,6 @@
 import { expect } from "chai";
 import * as build from "../../../deploy/functions/build";
+import { ParamValue } from "../../../deploy/functions/params";
 
 describe("toBackend", () => {
   it("populates backend info from Build", () => {
@@ -110,4 +111,49 @@ describe("toBackend", () => {
       ).to.have.members(["service-account-1@", "service-account-2@"]);
     }
   });
+
+  it("populates multiple param values", () => {
+    const desiredBuild: build.Build = build.of({
+      func: {
+        platform: "gcfv2",
+        region: ["us-central1"],
+        project: "project",
+        runtime: "nodejs16",
+        entryPoint: "func",
+        maxInstances: "{{ params.maxinstances }}",
+        minInstances: "{{ params.mininstances }}",
+        serviceAccount: "{{ params.serviceaccount }}",
+        vpc: {
+          connector: "projects/project/locations/region/connectors/connector",
+          egressSettings: "PRIVATE_RANGES_ONLY",
+        },
+        ingressSettings: "ALLOW_ALL",
+        labels: {
+          test: "testing",
+        },
+        httpsTrigger: {
+          invoker: ["service-account-2@", "service-account-3@"],
+        },
+      },
+    });
+    const backend = build.toBackend(desiredBuild, {
+      maxinstances: new ParamValue("42", false, { number: true }),
+      mininstances: new ParamValue("1", false, { number: true }),
+      serviceaccount: new ParamValue("service-account-1@", false, { string: true }),
+    });
+    expect(Object.keys(backend.endpoints).length).to.equal(1);
+    const endpointDef = Object.values(backend.endpoints)[0];
+    expect(endpointDef).to.not.equal(undefined);
+    if (endpointDef) {
+      expect(endpointDef.func.id).to.equal("func");
+      expect(endpointDef.func.project).to.equal("project");
+      expect(endpointDef.func.region).to.equal("us-central1");
+      expect(endpointDef.func.maxInstances).to.equal(42);
+      expect(endpointDef.func.minInstances).to.equal(1);
+      expect(endpointDef.func.serviceAccount).to.equal("service-account-1@");
+      expect(
+        "httpsTrigger" in endpointDef.func ? endpointDef.func.httpsTrigger.invoker : []
+      ).to.have.members(["service-account-2@", "service-account-3@"]);
+    }
+  });
 });