diff --git a/go/packages/golist.go b/go/packages/golist.go
index 71daa8bd4df..d9be410aa1a 100644
--- a/go/packages/golist.go
+++ b/go/packages/golist.go
@@ -841,6 +841,7 @@ func (state *golistState) cfgInvocation() gocommand.Invocation {
 		Env:        cfg.Env,
 		Logf:       cfg.Logf,
 		WorkingDir: cfg.Dir,
+		Overlay:    cfg.goListOverlayFile,
 	}
 }
 
@@ -849,18 +850,6 @@ func (state *golistState) invokeGo(verb string, args ...string) (*bytes.Buffer,
 	cfg := state.cfg
 
 	inv := state.cfgInvocation()
-
-	// Since go1.16, `go list` accepts overlays directly via the
-	// -overlay flag. (The check for "list" avoids unnecessarily
-	// writing the overlay file for a 'go env' command.)
-	if verb == "list" {
-		overlay, cleanup, err := gocommand.WriteOverlays(cfg.Overlay)
-		if err != nil {
-			return nil, err
-		}
-		defer cleanup()
-		inv.Overlay = overlay
-	}
 	inv.Verb = verb
 	inv.Args = args
 	gocmdRunner := cfg.gocmdRunner
diff --git a/go/packages/packages.go b/go/packages/packages.go
index ec4ade6540e..34306ddd390 100644
--- a/go/packages/packages.go
+++ b/go/packages/packages.go
@@ -133,7 +133,14 @@ const (
 
 // A Config specifies details about how packages should be loaded.
 // The zero value is a valid configuration.
+//
 // Calls to Load do not modify this struct.
+//
+// TODO(adonovan): #67702: this is currently false: in fact,
+// calls to [Load] do not modify the public fields of this struct, but
+// may modify hidden fields, so concurrent calls to [Load] must not
+// use the same Config. But perhaps we should reestablish the
+// documented invariant.
 type Config struct {
 	// Mode controls the level of information returned for each package.
 	Mode LoadMode
@@ -222,6 +229,10 @@ type Config struct {
 	// consistent package metadata about unsaved files. However,
 	// drivers may vary in their level of support for overlays.
 	Overlay map[string][]byte
+
+	// goListOverlayFile is the JSON file that encodes the Overlay
+	// mapping, used by 'go list -overlay=...'
+	goListOverlayFile string
 }
 
 // Load loads and returns the Go packages named by the given patterns.
@@ -316,6 +327,17 @@ func defaultDriver(cfg *Config, patterns ...string) (*DriverResponse, bool, erro
 		// (fall through)
 	}
 
+	// go list fallback
+	//
+	// Write overlays once, as there are many calls
+	// to 'go list' (one per chunk plus others too).
+	overlay, cleanupOverlay, err := gocommand.WriteOverlays(cfg.Overlay)
+	if err != nil {
+		return nil, false, err
+	}
+	defer cleanupOverlay()
+	cfg.goListOverlayFile = overlay
+
 	response, err := callDriverOnChunks(goListDriver, cfg, chunks)
 	if err != nil {
 		return nil, false, err
diff --git a/go/packages/packages_test.go b/go/packages/packages_test.go
index 294f058e81a..2a2e5a01054 100644
--- a/go/packages/packages_test.go
+++ b/go/packages/packages_test.go
@@ -3024,3 +3024,38 @@ func TestLoadEitherSucceedsOrFails(t *testing.T) {
 		t.Errorf("Load returned %d packages (want 1) and no error", len(initial))
 	}
 }
+
+// TestLoadOverlayGoMod ensures that overlays containing go.mod files
+// are effective for all 'go list' calls made by go/packages (#67644).
+func TestLoadOverlayGoMod(t *testing.T) {
+	testenv.NeedsGoBuild(t)
+
+	cwd, _ := os.Getwd()
+
+	// This test ensures that the overlaid go.mod file is seen by
+	// all runs of 'go list', in particular the early run that
+	// enumerates the modules: if the go.mod file were absent,
+	// it would ascend to the parent directory (x/tools) and
+	// then (falsely) report inconsistent vendoring.
+	//
+	// (Ideally the testdata would be constructed from nothing
+	// rather than rely on the go/packages source tree, but it is
+	// turned out to a bigger project than bargained for.)
+	cfg := &packages.Config{
+		Mode: packages.LoadSyntax,
+		Overlay: map[string][]byte{
+			filepath.Join(cwd, "go.mod"): []byte("module example.com\ngo 1.0"),
+		},
+		Env: append(os.Environ(), "GOFLAGS=-mod=vendor", "GOWORK=off"),
+	}
+
+	pkgs, err := packages.Load(cfg, "./testdata")
+	if err != nil {
+		t.Fatal(err) // (would previously fail here with "inconsistent vendoring")
+	}
+	got := fmt.Sprint(pkgs)
+	want := `[./testdata]`
+	if got != want {
+		t.Errorf("Load: got %s, want %v", got, want)
+	}
+}