diff --git a/src/main/__tests__/install-sonar-scanner.test.js b/src/main/__tests__/install-sonar-scanner.test.js
index 78e2582..43105ef 100644
--- a/src/main/__tests__/install-sonar-scanner.test.js
+++ b/src/main/__tests__/install-sonar-scanner.test.js
@@ -22,6 +22,7 @@ import assert from "node:assert/strict";
 import { describe, it, mock } from "node:test";
 
 const SCANNER_VERSION = "6.2.0.4584";
+const SCANNER_SEMVER_VERSION = "6.2.0-build.4584";
 const BINARIES_URL = "https://my.artifactory.example.com/sonar-scanner-cli";
 const BINARY_DOWNLOAD_URL = `${BINARIES_URL}/sonar-scanner-cli-${SCANNER_VERSION}-linux-x64.zip`;
 
@@ -31,6 +32,7 @@ function mockUtils(t) {
       getPlatformFlavor: mock.fn(() => "linux-x64"),
       getScannerDownloadURL: mock.fn(() => BINARY_DOWNLOAD_URL),
       scannerDirName: mock.fn(() => `sonar-scanner-${SCANNER_VERSION}-linux-x64`),
+      toSemVer: mock.fn(() => SCANNER_SEMVER_VERSION),
     },
   });
 }
@@ -171,6 +173,50 @@ describe("installSonarScanner", () => {
     assert.equal(downloadCalls[0].auth, "Bearer mytoken");
   });
 
+  it("should use semver-compatible version for tool-cache find and cacheDir", async (t) => {
+    const findFn = mock.fn(() => null);
+    const cacheDirFn = mock.fn(async () => "/tmp/cached");
+
+    mockUtils(t);
+
+    t.mock.module("@actions/tool-cache", {
+      namedExports: {
+        find: findFn,
+        downloadTool: mock.fn(async () => "/tmp/downloaded"),
+        extractZip: mock.fn(async () => "/tmp/extracted"),
+        cacheDir: cacheDirFn,
+      },
+    });
+
+    t.mock.module("@actions/core", {
+      namedExports: {
+        info: mock.fn(),
+        warning: mock.fn(),
+        addPath: mock.fn(),
+      },
+    });
+
+    t.mock.module("../gpg-verification.js", {
+      namedExports: {
+        verifySignature: mock.fn(async () => {}),
+      },
+    });
+
+    const { installSonarScanner } = await import(
+      `../install-sonar-scanner.js?test=semver-version`
+    );
+
+    await installSonarScanner({
+      scannerVersion: SCANNER_VERSION,
+      scannerBinariesUrl: BINARIES_URL,
+    });
+
+    assert.equal(findFn.mock.calls[0].arguments[1], SCANNER_SEMVER_VERSION,
+      "tc.find should be called with semver-compatible version");
+    assert.equal(cacheDirFn.mock.calls[0].arguments[2], SCANNER_SEMVER_VERSION,
+      "tc.cacheDir should be called with semver-compatible version");
+  });
+
   it("should use cached tool when available and skip download", async (t) => {
     const downloadToolFn = mock.fn();
 
diff --git a/src/main/__tests__/utils.test.js b/src/main/__tests__/utils.test.js
index cc88650..b379131 100644
--- a/src/main/__tests__/utils.test.js
+++ b/src/main/__tests__/utils.test.js
@@ -22,6 +22,7 @@ import {
   getPlatformFlavor,
   getScannerDownloadURL,
   scannerDirName,
+  toSemVer,
 } from "../utils.js";
 
 describe("getPlatformFlavor", () => {
@@ -97,3 +98,22 @@ describe("scannerDirName", () => {
     );
   });
 });
+
+describe("toSemVer", () => {
+  it("converts 4-part version to semver pre-release format", () => {
+    assert.equal(toSemVer("8.0.1.6346"), "8.0.1-build.6346");
+  });
+
+  it("leaves 3-part semver version unchanged", () => {
+    assert.equal(toSemVer("8.0.1"), "8.0.1");
+  });
+
+  it("leaves version with pre-release identifier unchanged", () => {
+    assert.equal(toSemVer("7.2.0-SNAPSHOT"), "7.2.0-SNAPSHOT");
+  });
+
+  it("converts different 4-part versions correctly", () => {
+    assert.equal(toSemVer("6.2.0.4584"), "6.2.0-build.4584");
+    assert.equal(toSemVer("8.1.0.6389"), "8.1.0-build.6389");
+  });
+});
diff --git a/src/main/install-sonar-scanner.js b/src/main/install-sonar-scanner.js
index 1d74798..13dd179 100644
--- a/src/main/install-sonar-scanner.js
+++ b/src/main/install-sonar-scanner.js
@@ -24,6 +24,7 @@ import {
   getPlatformFlavor,
   getScannerDownloadURL,
   scannerDirName,
+  toSemVer,
 } from "./utils.js";
 import { verifySignature } from "./gpg-verification.js";
 
@@ -39,9 +40,10 @@ export async function installSonarScanner({
   skipSignatureVerification = false,
 }) {
   const flavor = getPlatformFlavor(os.platform(), os.arch());
+  const semVerVersion = toSemVer(scannerVersion);
 
   // Check if tool is already cached
-  let toolDir = tc.find(TOOLNAME, scannerVersion, flavor);
+  let toolDir = tc.find(TOOLNAME, semVerVersion, flavor);
 
   if (!toolDir) {
     core.info(
@@ -84,7 +86,7 @@ export async function installSonarScanner({
       scannerDirName(scannerVersion, flavor)
     );
 
-    toolDir = await tc.cacheDir(scannerPath, TOOLNAME, scannerVersion, flavor);
+    toolDir = await tc.cacheDir(scannerPath, TOOLNAME, semVerVersion, flavor);
 
     core.info(`Sonar Scanner CLI cached to: ${toolDir}`);
   } else {
diff --git a/src/main/utils.js b/src/main/utils.js
index 87ba8b9..a53e653 100644
--- a/src/main/utils.js
+++ b/src/main/utils.js
@@ -51,3 +51,16 @@ export function getScannerDownloadURL({
 
 export const scannerDirName = (version, flavor) =>
   `sonar-scanner-${version}-${flavor}`;
+
+/**
+ * Converts a 4-part version string (e.g. "8.0.1.6346") to a SemVer 2.0 compatible
+ * string (e.g. "8.0.1-build.6346") for use with GitHub's tool-cache library,
+ * which requires SemVer-compliant version strings.
+ */
+export function toSemVer(version) {
+  const parts = version.split(".");
+  if (parts.length === 4) {
+    return `${parts[0]}.${parts[1]}.${parts[2]}-build.${parts[3]}`;
+  }
+  return version;
+}