diff --git a/doc/api/zlib.md b/doc/api/zlib.md
index f32715ba6cc6b2..a94bc7569d1c70 100644
--- a/doc/api/zlib.md
+++ b/doc/api/zlib.md
@@ -784,8 +784,9 @@ const stream = zlib.createZstdCompress({
 #### Pledged Source Size
 
 It's possible to specify the expected total size of the uncompressed input via
-`opts.pledgedSrcSize`. If the size doesn't match at the end of the input,
-compression will fail with the code `ZSTD_error_srcSize_wrong`.
+`opts.pledgedSrcSize`, which must be a non-negative safe integer. If the size
+doesn't match at the end of the input, compression will fail with the code
+`ZSTD_error_srcSize_wrong`.
 
 #### Decompressor options
 
@@ -1923,7 +1924,8 @@ added: v25.9.0
       `ZSTD_btultra2`.
       See the [Zstd compressor options][] in the zlib documentation for the
       full list.
-  * `pledgedSrcSize` {number} Expected uncompressed size (optional hint).
+  * `pledgedSrcSize` {number} Expected uncompressed size as a non-negative safe
+    integer (optional hint).
   * `dictionary` {Buffer|TypedArray|DataView}
 * Returns: {Object} A stateful transform.
 
diff --git a/lib/internal/streams/iter/transform.js b/lib/internal/streams/iter/transform.js
index 9782f5f50ebf2c..be286560ff238f 100644
--- a/lib/internal/streams/iter/transform.js
+++ b/lib/internal/streams/iter/transform.js
@@ -41,6 +41,7 @@ const { kValidatedTransform } = require('internal/streams/iter/types');
 const {
   checkRangesOrGetDefault,
   validateFiniteNumber,
+  validateInteger,
   validateObject,
 } = require('internal/validators');
 const binding = internalBinding('zlib');
@@ -258,14 +259,7 @@ function createZstdHandle(mode, options, processCallback, onError) {
 
   const pledgedSrcSize = options.pledgedSrcSize;
   if (pledgedSrcSize !== undefined) {
-    if (typeof pledgedSrcSize !== 'number' || NumberIsNaN(pledgedSrcSize)) {
-      throw new ERR_INVALID_ARG_TYPE('options.pledgedSrcSize', 'number',
-                                     pledgedSrcSize);
-    }
-    if (pledgedSrcSize < 0) {
-      throw new ERR_OUT_OF_RANGE('options.pledgedSrcSize', '>= 0',
-                                 pledgedSrcSize);
-    }
+    validateInteger(pledgedSrcSize, 'options.pledgedSrcSize', 0);
   }
 
   const handle = isCompress ?
diff --git a/lib/zlib.js b/lib/zlib.js
index 47726337cf720d..42b983717df993 100644
--- a/lib/zlib.js
+++ b/lib/zlib.js
@@ -68,6 +68,7 @@ const {
   checkRangesOrGetDefault,
   validateBoolean,
   validateFunction,
+  validateInteger,
   validateUint32,
   validateFiniteNumber,
 } = require('internal/validators');
@@ -926,11 +927,14 @@ class Zstd extends ZlibBase {
       });
     }
 
+    const pledgedSrcSize = opts?.pledgedSrcSize;
+    if (pledgedSrcSize !== undefined) {
+      validateInteger(pledgedSrcSize, 'options.pledgedSrcSize', 0);
+    }
+
     const handle = mode === ZSTD_COMPRESS ?
       new binding.ZstdCompress() : new binding.ZstdDecompress();
 
-    const pledgedSrcSize = opts?.pledgedSrcSize ?? undefined;
-
     const writeState = new Uint32Array(2);
 
     handle.init(
diff --git a/src/node_zlib.cc b/src/node_zlib.cc
index 95201624cfa2fa..cecaf0543855f8 100644
--- a/src/node_zlib.cc
+++ b/src/node_zlib.cc
@@ -939,9 +939,6 @@ class ZstdStream final : public CompressionStream<CompressionContext> {
   }
 
   static void Init(const FunctionCallbackInfo<Value>& args) {
-    Environment* env = Environment::GetCurrent(args);
-    Local<Context> context = env->context();
-
     CHECK((args.Length() == 4 || args.Length() == 5) &&
           "init(params, pledgedSrcSize, writeResult, writeCallback[, "
           "dictionary])");
@@ -958,19 +955,24 @@ class ZstdStream final : public CompressionStream<CompressionContext> {
     wrap->InitStream(write_result, write_js_callback);
 
     uint64_t pledged_src_size = ZSTD_CONTENTSIZE_UNKNOWN;
-    if (args[1]->IsNumber()) {
-      int64_t signed_pledged_src_size;
-      if (!args[1]->IntegerValue(context).To(&signed_pledged_src_size)) {
-        THROW_ERR_INVALID_ARG_VALUE(wrap->env(),
-                                    "pledgedSrcSize should be an integer");
+    if (!args[1]->IsUndefined()) {
+      if (!args[1]->IsNumber()) {
+        THROW_ERR_INVALID_ARG_TYPE(wrap->env(),
+                                   "pledgedSrcSize must be a number");
+        return;
+      }
+      if (!IsSafeJsInt(args[1])) {
+        THROW_ERR_OUT_OF_RANGE(wrap->env(),
+                               "pledgedSrcSize must be a safe integer");
         return;
       }
+      const int64_t signed_pledged_src_size = args[1].As<Integer>()->Value();
       if (signed_pledged_src_size < 0) {
-        THROW_ERR_INVALID_ARG_VALUE(wrap->env(),
-                                    "pledgedSrcSize may not be negative");
+        THROW_ERR_OUT_OF_RANGE(wrap->env(),
+                               "pledgedSrcSize must be non-negative");
         return;
       }
-      pledged_src_size = signed_pledged_src_size;
+      pledged_src_size = static_cast<uint64_t>(signed_pledged_src_size);
     }
 
     AllocScope alloc_scope(wrap);
diff --git a/test/parallel/test-stream-iter-validation.js b/test/parallel/test-stream-iter-validation.js
index 08eeaeee685656..c2917bcd42b8fe 100644
--- a/test/parallel/test-stream-iter-validation.js
+++ b/test/parallel/test-stream-iter-validation.js
@@ -352,7 +352,16 @@ async function testAsyncValidation() {
 
   // Zstd pledgedSrcSize
   await assert.rejects(consume(compressZstd({ pledgedSrcSize: 'bad' })), TYPE);
-  await assert.rejects(consume(compressZstd({ pledgedSrcSize: -1 })), RANGE);
+  for (const pledgedSrcSize of [
+    NaN,
+    Infinity,
+    -Infinity,
+    1.9,
+    -1,
+    Number.MAX_SAFE_INTEGER + 1,
+  ]) {
+    await assert.rejects(consume(compressZstd({ pledgedSrcSize })), RANGE);
+  }
 }
 
 // =============================================================================
diff --git a/test/parallel/test-zlib-zstd-pledged-src-size.js b/test/parallel/test-zlib-zstd-pledged-src-size.js
index b1e32e14ae732a..4a5f27394c6609 100644
--- a/test/parallel/test-zlib-zstd-pledged-src-size.js
+++ b/test/parallel/test-zlib-zstd-pledged-src-size.js
@@ -35,3 +35,39 @@ compressWithPledgedSrcSize({ pledgedSrcSize: 42, actualSrcSize: 0 });
 compressWithPledgedSrcSize({ pledgedSrcSize: 42, actualSrcSize: 13 });
 
 compressWithPledgedSrcSize({ pledgedSrcSize: 42, actualSrcSize: 42 });
+
+function assertInvalidPledgedSrcSize(pledgedSrcSize, expected) {
+  assert.throws(
+    () => zlib.createZstdCompress({ pledgedSrcSize }),
+    expected,
+  );
+  assert.throws(
+    () => zlib.zstdCompressSync('', { pledgedSrcSize }),
+    expected,
+  );
+}
+
+for (const pledgedSrcSize of ['1', null]) {
+  assertInvalidPledgedSrcSize(pledgedSrcSize, {
+    name: 'TypeError',
+    code: 'ERR_INVALID_ARG_TYPE',
+  });
+}
+
+for (const pledgedSrcSize of [
+  NaN,
+  Infinity,
+  -Infinity,
+  1.9,
+  -1,
+  Number.MAX_SAFE_INTEGER + 1,
+]) {
+  assertInvalidPledgedSrcSize(pledgedSrcSize, {
+    name: 'RangeError',
+    code: 'ERR_OUT_OF_RANGE',
+  });
+}
+
+zlib.createZstdCompress({
+  pledgedSrcSize: Number.MAX_SAFE_INTEGER,
+}).destroy();