diff --git a/test/typecheck/main.go b/test/typecheck/main.go
index 411a945d47..2df32f41c8 100644
--- a/test/typecheck/main.go
+++ b/test/typecheck/main.go
@@ -24,6 +24,7 @@ import (
 	"go/build"
 	"go/parser"
 	"go/token"
+	"io"
 	"log"
 	"os"
 	"path/filepath"
@@ -60,6 +61,8 @@ var (
 		"linux/arm64", "linux/ppc64le",
 		"linux/s390x", "darwin/386",
 	}
+	darwinPlatString  = "darwin/386,darwin/amd64"
+	windowsPlatString = "windows/386,windows/amd64"
 )
 
 type analyzer struct {
@@ -69,6 +72,7 @@ type analyzer struct {
 	failed    bool
 	platform  string
 	donePaths map[string]interface{}
+	errors    []string
 }
 
 func newAnalyzer(platform string) *analyzer {
@@ -120,11 +124,19 @@ func (a *analyzer) handleError(err error) {
 			return
 		}
 	}
-	// TODO(rmmh): dedup errors across platforms?
-	fmt.Fprintf(os.Stderr, "%sERROR(%s) %s\n", logPrefix, a.platform, err)
+	a.errors = append(a.errors, err.Error())
+	if *serial {
+		fmt.Fprintf(os.Stderr, "%sERROR(%s) %s\n", logPrefix, a.platform, err)
+	}
 	a.failed = true
 }
 
+func (a *analyzer) dumpAndResetErrors() []string {
+	es := a.errors
+	a.errors = nil
+	return es
+}
+
 // collect extracts test metadata from a file.
 func (a *analyzer) collect(dir string) {
 	if _, ok := a.donePaths[dir]; ok {
@@ -262,6 +274,51 @@ func (c *collector) handlePath(path string, info os.FileInfo, err error) error {
 	return nil
 }
 
+type analyzerResult struct {
+	platform string
+	dir      string
+	errors   []string
+}
+
+func dedupeErrors(out io.Writer, results chan analyzerResult, nDirs, nPlatforms int) {
+	pkgRes := make(map[string][]analyzerResult)
+	for done := 0; done < nDirs; {
+		res := <-results
+		pkgRes[res.dir] = append(pkgRes[res.dir], res)
+		if len(pkgRes[res.dir]) != nPlatforms {
+			continue // expect more results for dir
+		}
+		done++
+		// Collect list of platforms for each error
+		errPlats := map[string][]string{}
+		for _, res := range pkgRes[res.dir] {
+			for _, err := range res.errors {
+				errPlats[err] = append(errPlats[err], res.platform)
+			}
+		}
+		// Print each error (in the same order!) once.
+		for _, res := range pkgRes[res.dir] {
+			for _, err := range res.errors {
+				if errPlats[err] == nil {
+					continue // already printed
+				}
+				sort.Strings(errPlats[err])
+				plats := strings.Join(errPlats[err], ",")
+				if len(errPlats[err]) == len(crossPlatforms) {
+					plats = "all"
+				} else if plats == darwinPlatString {
+					plats = "darwin"
+				} else if plats == windowsPlatString {
+					plats = "windows"
+				}
+				fmt.Fprintf(out, "%sERROR(%s) %s\n", logPrefix, plats, err)
+				delete(errPlats, err)
+			}
+		}
+		delete(pkgRes, res.dir)
+	}
+}
+
 func main() {
 	flag.Parse()
 	args := flag.Args()
@@ -296,6 +353,15 @@ func main() {
 	var processedDirs int64
 	var currentWork int64 // (dir_index << 8) | platform_index
 	statuses := make([]int, len(ps))
+	var results chan analyzerResult
+	if !*serial {
+		results = make(chan analyzerResult)
+		wg.Add(1)
+		go func() {
+			dedupeErrors(os.Stderr, results, len(c.dirs), len(ps))
+			wg.Done()
+		}()
+	}
 	for i, p := range ps {
 		wg.Add(1)
 		fn := func(i int, p string) {
@@ -305,6 +371,9 @@ func main() {
 				a.collect(dir)
 				atomic.AddInt64(&processedDirs, 1)
 				atomic.StoreInt64(&currentWork, int64(n<<8|i))
+				if results != nil {
+					results <- analyzerResult{p, dir, a.dumpAndResetErrors()}
+				}
 			}
 			if a.failed {
 				statuses[i] = 1
diff --git a/test/typecheck/main_test.go b/test/typecheck/main_test.go
index 803963f2a8..9b1fb830d5 100644
--- a/test/typecheck/main_test.go
+++ b/test/typecheck/main_test.go
@@ -17,6 +17,7 @@ limitations under the License.
 package main
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"go/ast"
@@ -155,3 +156,38 @@ func TestHandlePath(t *testing.T) {
 		t.Error("should skip vendor")
 	}
 }
+
+func TestDedupeErrors(t *testing.T) {
+	testcases := []struct {
+		nPlatforms int
+		results    []analyzerResult
+		expected   string
+	}{
+		{1, []analyzerResult{}, ""},
+		{1, []analyzerResult{{"linux/arm", "test", nil}}, ""},
+		{1, []analyzerResult{
+			{"linux/arm", "test", []string{"a"}}},
+			"ERROR(linux/arm) a\n"},
+		{3, []analyzerResult{
+			{"linux/arm", "test", []string{"a"}},
+			{"windows/386", "test", []string{"b"}},
+			{"windows/amd64", "test", []string{"b", "c"}}},
+			"ERROR(linux/arm) a\n" +
+				"ERROR(windows) b\n" +
+				"ERROR(windows/amd64) c\n"},
+	}
+	for _, tc := range testcases {
+		out := &bytes.Buffer{}
+		results := make(chan analyzerResult, len(tc.results))
+		for _, res := range tc.results {
+			results <- res
+		}
+		close(results)
+		dedupeErrors(out, results, len(tc.results)/tc.nPlatforms, tc.nPlatforms)
+		outString := out.String()
+		if outString != tc.expected {
+			t.Errorf("dedupeErrors(%v) = '%s', expected '%s'",
+				tc.results, outString, tc.expected)
+		}
+	}
+}