diff --git a/e2e/e2e_credentials_test.go b/e2e/e2e_credentials_test.go
new file mode 100644
index 0000000000..d79b465e29
--- /dev/null
+++ b/e2e/e2e_credentials_test.go
@@ -0,0 +1,51 @@
+//go:build e2e
+// +build e2e
+
+package e2e
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"strings"
+	"testing"
+)
+
+// Test that FUNC_USERNAME/FUNC_PASSWORD are picked up by all pushers
+// by asserting the pusher's log message includes the provided username.
+// This test runs for host, pack, and s2i builders automatically.
+func TestCredentials_DockerPusher_EnvUsed(t *testing.T) {
+	for _, builder := range []string{"host", "pack", "s2i"} {
+		t.Run(builder, func(t *testing.T) {
+			name := fmt.Sprintf("func-e2e-creds-docker-%s", builder)
+			_ = fromCleanEnv(t, name)
+
+			// Provide credentials via env (what issue #3314 validates)
+			const user = "e2euser"
+			const pass = "e2epass"
+			os.Setenv("FUNC_USERNAME", user)
+			os.Setenv("FUNC_PASSWORD", pass)
+
+			// Init a simple function
+			if err := newCmd(t, "init", "-l=go").Run(); err != nil {
+				t.Fatal(err)
+			}
+
+			// Build and push; capture stderr to assert credentials log
+			cmd := newCmd(t, "build", "--builder", builder, "--push", "--registry", Registry)
+			var stderr bytes.Buffer
+			cmd.Stderr = &stderr
+			if err := cmd.Run(); err != nil {
+				t.Fatalf("build --push failed: %v\nerrOut: %s", err, stderr.String())
+			}
+
+			// docker pusher logs: Pushing function image to the registry %q using the %q user credentials
+			if !strings.Contains(stderr.String(), "using the \""+user+"\" user credentials") {
+				t.Fatalf("expected docker pusher to log username %q in stderr, got: %s", user, stderr.String())
+			}
+
+			// Clean local images/volumes to keep CI tidy
+			cleanImages(t, name)
+		})
+	}
+}
diff --git a/pkg/oci/pusher.go b/pkg/oci/pusher.go
index 07b97d4791..f46b83c07d 100644
--- a/pkg/oci/pusher.go
+++ b/pkg/oci/pusher.go
@@ -99,6 +99,17 @@ func (p *Pusher) Push(ctx context.Context, f fn.Function) (digest string, err er
 		return
 	}
 
+	// Extract registry from image to log which registry we're pushing to
+	registry := "registry"
+	if ref, err := name.ParseReference(f.Build.Image); err == nil {
+		registry = ref.Context().RegistryStr()
+	}
+
+	// Log credentials being used (consistent with docker pusher)
+	if credentials.Username != "" {
+		fmt.Fprintf(os.Stderr, "Pushing function image to the registry %q using the %q user credentials\n", registry, credentials.Username)
+	}
+
 	var opts []name.Option
 	if p.Insecure {
 		opts = append(opts, name.Insecure)