diff --git a/internal/app/discussion_search.go b/internal/app/discussion_search.go
index 728ff32a..62a6803e 100644
--- a/internal/app/discussion_search.go
+++ b/internal/app/discussion_search.go
@@ -37,6 +37,10 @@ func (a *application) discussionSearchCommand(pulls bool) *cobra.Command {
 		if err != nil {
 			return err
 		}
+		milestones, err := nameFilter("milestone", opts.Milestones)
+		if err != nil {
+			return err
+		}
 		target, err := a.resolve(cmd.Context(), false)
 		if err != nil {
 			return err
@@ -50,13 +54,15 @@ func (a *application) discussionSearchCommand(pulls bool) *cobra.Command {
 		if opts.Team != "" && target.Repo != "" {
 			return clierr.Wrap(clierr.Usage, errors.New("--team requires instance-wide search; omit --repo or TEA_REPO"))
 		}
-		if len(labelNames) > 0 {
-			if target.Repo != "" {
-				if err := (services.Labels{Client: target.client, Repository: target.Repo}).RequireFilterNames(cmd.Context(), labelNames); err != nil {
-					return err
-				}
+		if target.Repo != "" {
+			if opts.Labels, opts.Milestones, err = issueFilters(cmd, target, labelNames, milestones); err != nil {
+				return err
+			}
+		} else if len(labelNames)+len(milestones) > 0 {
+			opts.Labels, opts.Milestones = strings.Join(labelNames, ","), strings.Join(milestones, ",")
+			if _, err := fmt.Fprintln(cmd.ErrOrStderr(), "warning: instance-wide search ignores --label and --milestone values that match nothing; pass --repo to check them"); err != nil {
+				return err
 			}
-			opts.Labels = strings.Join(labelNames, ",")
 		}
 		opts.Query = strings.Join(args, " ")
 		items, err := (services.Issues{Client: target.client, Repository: target.Repo}).Search(cmd.Context(), opts)
diff --git a/internal/app/issue_filters_test.go b/internal/app/issue_filters_test.go
index 9798c7cf..ac602801 100644
--- a/internal/app/issue_filters_test.go
+++ b/internal/app/issue_filters_test.go
@@ -128,3 +128,56 @@ func TestIssueListWithoutRepoPointsToSearch(t *testing.T) {
 	require.ErrorContains(t, err, "tea search issue")
 	require.Empty(t, out.String())
 }
+
+func TestIssueMilestoneFiltersRejectUnknownMilestones(t *testing.T) {
+	var listed []string
+	server := newAuthenticatedServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.URL.Path {
+		case "/api/v1/repos/alice/project/milestones":
+			require.Equal(t, "all", r.URL.Query().Get("state"))
+			if r.URL.Query().Get("page") == "1" {
+				_, _ = w.Write([]byte(`[{"id":1,"title":"v1.0"},{"id":2,"title":"2026","state":"closed"}]`))
+				return
+			}
+			_, _ = w.Write([]byte(`[]`))
+		case "/api/v1/repos/alice/project/issues", "/api/v1/repos/issues/search":
+			listed = append(listed, r.URL.Path+"?milestones="+r.URL.Query().Get("milestones"))
+			_, _ = w.Write([]byte(`[]`))
+		default:
+			t.Errorf("unexpected %s %s", r.Method, r.URL.Path)
+		}
+	}))
+	defer server.Close()
+	deps, out, diagnostics := serverDeps(t, server.URL)
+	for _, test := range []struct {
+		args []string
+		want string
+	}{
+		{[]string{"issue", "list", "--milestone", "nope"}, `milestone "nope" not found in alice/project`},
+		{[]string{"issue", "list", "--milestone", "999"}, "milestone 999 not found in alice/project"},
+		{[]string{"issue", "list", "--milestone", "v1.0,nope"}, `milestone "nope" not found`},
+		{[]string{"search", "issue", "--milestone", "nope"}, `milestone "nope" not found in alice/project`},
+		{[]string{"search", "pr", "--milestone", "nope"}, `milestone "nope" not found in alice/project`},
+	} {
+		err := Execute(context.Background(), deps, append(test.args, "-R", "alice/project", "--json"))
+		require.Equal(t, clierr.Failure, clierr.ExitCode(err), "%v", err)
+		require.ErrorContains(t, err, test.want)
+	}
+	require.Empty(t, listed)
+	require.Empty(t, out.String())
+	for _, args := range [][]string{
+		{"issue", "list", "-R", "alice/project", "--milestone", "v1.0,2026"},
+		{"issue", "list", "-R", "alice/project", "--milestone", "1"},
+		{"search", "issue", "-R", "alice/project", "--milestone", "V1.0"},
+		{"search", "issue", "--milestone", "nope"},
+	} {
+		require.NoError(t, Execute(context.Background(), deps, append(args, "--json")))
+	}
+	require.Equal(t, []string{
+		"/api/v1/repos/alice/project/issues?milestones=1,2",
+		"/api/v1/repos/alice/project/issues?milestones=1",
+		"/api/v1/repos/alice/project/issues?milestones=1",
+		"/api/v1/repos/issues/search?milestones=nope",
+	}, listed)
+	require.Contains(t, diagnostics.String(), "pass --repo to check them")
+}
diff --git a/internal/app/issues.go b/internal/app/issues.go
index 9e2ea0a9..ab9504ae 100644
--- a/internal/app/issues.go
+++ b/internal/app/issues.go
@@ -114,6 +114,33 @@ func labelChoices(items []services.Label) []terminal.IssueLabelChoice {
 
 func issueLabel(n int64) string { return fmt.Sprintf("issue %d", n) }
 
+// nameFilter splits a comma-separated filter of kind, trimming entries and rejecting blanks.
+func nameFilter(kind, raw string) ([]string, error) {
+	if raw == "" {
+		return nil, nil
+	}
+	names := strings.Split(raw, ",")
+	return names, requireNames(kind, "", names)
+}
+
+// issueFilters checks the label and milestone filters of an issue listing in the target repository
+// and returns them as query values. Gitea ignores labels and milestones it cannot find, and lists
+// every issue when no filter value is left, so unknown names are errors.
+func issueFilters(cmd *cobra.Command, t target, labels, milestones []string) (labelQuery, milestoneQuery string, err error) {
+	if len(labels) > 0 {
+		if err := (services.Labels{Client: t.client, Repository: t.Repo}).RequireFilterNames(cmd.Context(), labels); err != nil {
+			return "", "", err
+		}
+	}
+	var ids []string
+	if len(milestones) > 0 {
+		if ids, err = (services.Milestones{Client: t.client, Repository: t.Repo}).FilterIDs(cmd.Context(), milestones); err != nil {
+			return "", "", err
+		}
+	}
+	return strings.Join(labels, ","), strings.Join(ids, ","), nil
+}
+
 // metadataFlags are the label and assignee flags shared by issue and pull request edits.
 type metadataFlags struct {
 	setLabels, addLabels, removeLabels          []string
@@ -206,6 +233,10 @@ func (a *application) issueCommand() *cobra.Command {
 		if err != nil {
 			return err
 		}
+		milestones, err := nameFilter("milestone", opts.Milestones)
+		if err != nil {
+			return err
+		}
 		target, err := a.resolve(cmd.Context(), true)
 		if err != nil {
 			if errors.Is(err, errRepositoryRequired) {
@@ -213,11 +244,8 @@ func (a *application) issueCommand() *cobra.Command {
 			}
 			return err
 		}
-		if len(labelNames) > 0 {
-			if err := (services.Labels{Client: target.client, Repository: target.Repo}).RequireFilterNames(cmd.Context(), labelNames); err != nil {
-				return err
-			}
-			opts.Labels = strings.Join(labelNames, ",")
+		if opts.Labels, opts.Milestones, err = issueFilters(cmd, target, labelNames, milestones); err != nil {
+			return err
 		}
 		items, more, err := (services.Issues{Client: target.client, Repository: target.Repo}).List(cmd.Context(), opts)
 		if err != nil {
diff --git a/internal/services/milestone_selection.go b/internal/services/milestone_selection.go
index f091ed2a..b97e2455 100644
--- a/internal/services/milestone_selection.go
+++ b/internal/services/milestone_selection.go
@@ -6,6 +6,7 @@ package services
 import (
 	"context"
 	"fmt"
+	"strconv"
 	"strings"
 )
 
@@ -14,7 +15,7 @@ func (s Milestones) ResolveName(ctx context.Context, name string) (int64, error)
 	if strings.TrimSpace(name) == "" {
 		return 0, fmt.Errorf("milestone name cannot be empty")
 	}
-	items, err := listAll(func(page int) ([]Milestone, error) { return s.List(ctx, "all", 100, page) })
+	items, err := s.All(ctx)
 	if err != nil {
 		return 0, err
 	}
@@ -33,3 +34,28 @@ func (s Milestones) ResolveName(ctx context.Context, name string) (int64, error)
 	}
 	return id, nil
 }
+
+// All returns the open and closed milestones of the repository.
+func (s Milestones) All(ctx context.Context) ([]Milestone, error) {
+	return listAll(func(page int) ([]Milestone, error) { return s.List(ctx, "all", 100, page) })
+}
+
+// FilterIDs resolves the milestones that filter an issue listing, each an ID or a title, to their
+// IDs. Gitea drops filter values that name no milestone and lists every issue when none is left,
+// so an unknown milestone is an error here.
+func (s Milestones) FilterIDs(ctx context.Context, values []string) ([]string, error) {
+	items, err := s.All(ctx)
+	if err != nil {
+		return nil, err
+	}
+	finder := NameOrID[Milestone]{Kind: "milestone", Scope: s.Repository, ID: func(m Milestone) int64 { return m.ID }, Name: func(m Milestone) string { return m.Title }}
+	ids := make([]string, len(values))
+	for i, value := range values {
+		milestone, err := finder.Find(items, value)
+		if err != nil {
+			return nil, err
+		}
+		ids[i] = strconv.FormatInt(milestone.ID, 10)
+	}
+	return ids, nil
+}