diff --git a/signing/signing.go b/signing/signing.go
index cf7c706f..c59998d7 100644
--- a/signing/signing.go
+++ b/signing/signing.go
@@ -33,6 +33,7 @@ import (
 
 	sigOpts "github.com/sigstore/cosign/v2/cmd/cosign/cli/options"
 	"github.com/sigstore/cosign/v2/cmd/cosign/cli/sign"
+	"github.com/sigstore/cosign/v2/pkg/cosign"
 
 	"github.com/ossf/scorecard-action/entrypoint"
 	"github.com/ossf/scorecard-action/options"
@@ -52,7 +53,8 @@ var (
 
 // Signing is a signing structure.
 type Signing struct {
-	token string
+	token          string
+	rekorTlogIndex int64
 }
 
 // New creates a new Signing instance.
@@ -78,6 +80,14 @@ func New(token string) (*Signing, error) {
 
 // SignScorecardResult signs the results file and uploads the attestation to the Rekor transparency log.
 func (s *Signing) SignScorecardResult(scorecardResultsFile string) error {
+	f, err := os.CreateTemp("", "bundle")
+	if err != nil {
+		return fmt.Errorf("creating temporary bundle file: %w", err)
+	}
+	bundlePath := f.Name()
+	f.Close()
+	defer os.Remove(bundlePath) // clean up
+
 	// Prepare settings for SignBlobCmd.
 	rootOpts := &sigOpts.RootOptions{Timeout: sigOpts.DefaultTimeout} // Just the timeout.
 	keyOpts := sigOpts.KeyOpts{
@@ -86,9 +96,9 @@ func (s *Signing) SignScorecardResult(scorecardResultsFile string) error {
 		OIDCIssuer:       sigOpts.DefaultOIDCIssuerURL, // OIDC provider to get ID token to auth for Fulcio.
 		OIDCClientID:     "sigstore",
 		SkipConfirmation: true, // skip cosign's privacy confirmation prompt as we run non-interactively
+		BundlePath:       bundlePath,
 	}
 
-	var err error
 	for _, backoff := range backoffSchedule {
 		// This command will use the provided OIDCIssuer to authenticate into Fulcio, which will generate the
 		// signing certificate on the scorecard result. This attestation is then uploaded to the Rekor transparency log.
@@ -107,6 +117,12 @@ func (s *Signing) SignScorecardResult(scorecardResultsFile string) error {
 		return fmt.Errorf("error signing payload: %w", err)
 	}
 
+	rekorTlogIndex, err := extractTlogIndex(bundlePath)
+	if err != nil {
+		return err
+	}
+	s.rekorTlogIndex = rekorTlogIndex
+
 	return nil
 }
 
@@ -143,10 +159,12 @@ func (s *Signing) ProcessSignature(jsonPayload []byte, repoName, repoRef string)
 		Result      string `json:"result"`
 		Branch      string `json:"branch"`
 		AccessToken string `json:"accessToken"`
+		TlogIndex   int64  `json:"tlogIndex"`
 	}{
 		Result:      string(jsonPayload),
 		Branch:      repoRef,
 		AccessToken: s.token,
+		TlogIndex:   s.rekorTlogIndex,
 	}
 
 	payloadBytes, err := json.Marshal(resultsPayload)
@@ -209,3 +227,16 @@ func postResults(endpoint *url.URL, payload []byte) error {
 
 	return nil
 }
+
+func extractTlogIndex(bundlePath string) (int64, error) {
+	contents, err := os.ReadFile(bundlePath)
+	if err != nil {
+		return 0, fmt.Errorf("reading cosign bundle file: %w", err)
+	}
+	var payload cosign.LocalSignedPayload
+	err = json.Unmarshal(contents, &payload)
+	if err != nil || payload.Bundle == nil {
+		return 0, fmt.Errorf("invalid cosign bundle file: %w", err)
+	}
+	return payload.Bundle.Payload.LogIndex, nil
+}
diff --git a/signing/signing_test.go b/signing/signing_test.go
index edfae6b0..22d53858 100644
--- a/signing/signing_test.go
+++ b/signing/signing_test.go
@@ -128,6 +128,45 @@ func TestProcessSignature(t *testing.T) {
 	}
 }
 
+func Test_extractTlogIndex(t *testing.T) {
+	t.Parallel()
+	tests := []struct {
+		name       string
+		bundlePath string
+		want       int64
+		wantErr    bool
+	}{
+		{
+			name:       "valid bundle",
+			bundlePath: "testdata/cosign.bundle",
+			want:       23548006,
+		},
+		{
+			name:       "invalid bundle",
+			bundlePath: "testdata/invalid-cosign.bundle",
+			wantErr:    true,
+		},
+		{
+			name:       "missing bundle",
+			bundlePath: "testdata/does-not-exist.bundle",
+			wantErr:    true,
+		},
+	}
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			got, err := extractTlogIndex(tt.bundlePath)
+			if (err != nil) != tt.wantErr {
+				t.Fatalf("unexpected err: %v, wantErr: %t", err, tt.wantErr)
+			}
+			if got != tt.want {
+				t.Errorf("wrong tlog index: got %d, wanted %d", got, tt.want)
+			}
+		})
+	}
+}
+
 //nolint:paralleltest // we are using t.Setenv
 func TestProcessSignature_retries(t *testing.T) {
 	tests := []struct {
diff --git a/signing/testdata/cosign.bundle b/signing/testdata/cosign.bundle
new file mode 100644
index 00000000..1822fbe4
--- /dev/null
+++ b/signing/testdata/cosign.bundle
@@ -0,0 +1 @@
+{"base64Signature":"MEUCIQD4rAvIUYt0WgrXVL6whlkgJerX2jyRNDct3AwWSsGdJgIgP0DCR56AM9FQD/aEnZwnNT1s22V8PW/ud0YHREr2n0U=","cert":"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","rekorBundle":{"SignedEntryTimestamp":"MEQCIG+3Fj1/9aYBP2fp9gbI9RpOc1/9aawUip5+aflRrtn/AiAo2nuSf3IIFwHpAgQL8eLkA3++gRiUkXDJzRZqjCXRhA==","Payload":{"body":"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","integratedTime":1686605136,"logIndex":23548006,"logID":"c0d23d6ad406973f9559f3ba2d1ca01f84147d8ffc5b8445c224f98b9591801d"}}}
\ No newline at end of file
diff --git a/signing/testdata/invalid-cosign.bundle b/signing/testdata/invalid-cosign.bundle
new file mode 100644
index 00000000..db71b2bc
--- /dev/null
+++ b/signing/testdata/invalid-cosign.bundle
@@ -0,0 +1 @@
+{"base64Signature":"MEUCIQD4rAvIUYt0WgrXVL6whlkgJerX2jyRNDct3AwWSsGdJgIgP0DCR56AM9FQD/aEnZwnNT1s22V8PW/ud0YHREr2n0U=","cert":"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"}
\ No newline at end of file