diff --git a/packages/@uppy/aws-s3-multipart/src/createSignedURL.js b/packages/@uppy/aws-s3-multipart/src/createSignedURL.js
index 593b327b6e..c7804c1681 100644
--- a/packages/@uppy/aws-s3-multipart/src/createSignedURL.js
+++ b/packages/@uppy/aws-s3-multipart/src/createSignedURL.js
@@ -76,6 +76,30 @@ async function hash (key, data) {
   return subtle.sign(algorithm, await generateHmacKey(key), ec.encode(data))
 }
 
+/**
+ * @see
+ *   https://github.com/smithy-lang/smithy-typescript/blob/main/packages/smithy-client/src/extended-encode-uri-component.ts
+ */
+function extendedEncodeURIComponent(str) {
+  return encodeURIComponent(str).replace(/[!'()*]/g, (c) =>
+    `%${c.charCodeAt(0).toString(16).toUpperCase()}`
+  )
+}
+
+class Query {
+  #params = []
+
+  append(key, value) {
+    this.#params.push([key, value])
+  }
+
+  toString() {
+    return this.#params
+      .map(([key, value]) => `${extendedEncodeURIComponent(key)}=${extendedEncodeURIComponent(value)}`)
+      .join('&')
+  }
+}
+
 /**
  * @see https://docs.aws.amazon.com/IAM/latest/UserGuide/create-signed-request.html
  * @param {Record<string,string>} param0
@@ -90,32 +114,32 @@ export default async function createSignedURL ({
 }) {
   const Service = 's3'
   const host = `${bucketName}.${Service}.${Region}.amazonaws.com`
-  const CanonicalUri = `/${encodeURI(Key)}`
+  const CanonicalUri = `/${Key.split('/').map(extendedEncodeURIComponent).join('/')}`
   const payload = 'UNSIGNED-PAYLOAD'
 
   const requestDateTime = new Date().toISOString().replace(/[-:]|\.\d+/g, '') // YYYYMMDDTHHMMSSZ
   const date = requestDateTime.slice(0, 8) // YYYYMMDD
   const scope = `${date}/${Region}/${Service}/aws4_request`
 
-  const url = new URL(`https://${host}${CanonicalUri}`)
+  const query = new Query();
   // N.B.: URL search params needs to be added in the ASCII order
-  url.searchParams.set('X-Amz-Algorithm', 'AWS4-HMAC-SHA256')
-  url.searchParams.set('X-Amz-Content-Sha256', payload)
-  url.searchParams.set('X-Amz-Credential', `${accountKey}/${scope}`)
-  url.searchParams.set('X-Amz-Date', requestDateTime)
-  url.searchParams.set('X-Amz-Expires', expires)
+  query.append('X-Amz-Algorithm', 'AWS4-HMAC-SHA256')
+  query.append('X-Amz-Content-Sha256', payload)
+  query.append('X-Amz-Credential', `${accountKey}/${scope}`)
+  query.append('X-Amz-Date', requestDateTime)
+  query.append('X-Amz-Expires', expires)
   // We are signing on the client, so we expect there's going to be a session token:
-  url.searchParams.set('X-Amz-Security-Token', sessionToken)
-  url.searchParams.set('X-Amz-SignedHeaders', 'host')
+  query.append('X-Amz-Security-Token', sessionToken)
+  query.append('X-Amz-SignedHeaders', 'host')
   // Those two are present only for Multipart Uploads:
-  if (partNumber) url.searchParams.set('partNumber', partNumber)
-  if (uploadId) url.searchParams.set('uploadId', uploadId)
-  url.searchParams.set('x-id', partNumber && uploadId ? 'UploadPart' : 'PutObject')
+  if (partNumber) query.append('partNumber', partNumber)
+  if (uploadId) query.append('uploadId', uploadId)
+  query.append('x-id', partNumber && uploadId ? 'UploadPart' : 'PutObject')
 
   // Step 1: Create a canonical request
   const canonical = createCanonicalRequest({
     CanonicalUri,
-    CanonicalQueryString: url.search.slice(1),
+    CanonicalQueryString: query.toString(),
     SignedHeaders: {
       host,
     },
@@ -141,7 +165,7 @@ export default async function createSignedURL ({
   const signature = arrayBufferToHexString(await hash(kSigning, stringToSign))
 
   // Step 5: Add the signature to the request
-  url.searchParams.set('X-Amz-Signature', signature)
+  query.append('X-Amz-Signature', signature)
 
-  return url
+  return new URL(`https://${host}${CanonicalUri}?${query.toString()}`)
 }
diff --git a/packages/@uppy/aws-s3-multipart/src/createSignedURL.test.js b/packages/@uppy/aws-s3-multipart/src/createSignedURL.test.js
index cfcb12742c..7687f1d24e 100644
--- a/packages/@uppy/aws-s3-multipart/src/createSignedURL.test.js
+++ b/packages/@uppy/aws-s3-multipart/src/createSignedURL.test.js
@@ -51,6 +51,8 @@ describe('createSignedURL', () => {
     )
   })
   it('should be able to sign multipart upload', async () => {
+    const url = new URL('https://example.com/?%21%27%28%29%2A')
+    console.log(url.search)
     const client = new S3Client(s3ClientOptions)
     const partNumber = 99
     const uploadId = 'dummyUploadId'
@@ -71,7 +73,40 @@ describe('createSignedURL', () => {
         UploadId: uploadId,
         PartNumber: partNumber,
         Key: 'some/key',
-      }, { expiresIn: 900 }))).searchParams.get('X-Amz-Signature'),
+      }), { expiresIn: 900 })).searchParams.get('X-Amz-Signature'),
+    )
+  })
+  it('should escape path and query as restricted to RFC 3986', async () => {
+    const client = new S3Client(s3ClientOptions)
+    const partNumber = 99
+    const uploadId = 'Upload!\'()*Id'
+    const Key = '!\'()*/!\'()*.ext'
+    const implResult =
+      await createSignedURL({
+        accountKey: s3ClientOptions.credentials.accessKeyId,
+        accountSecret: s3ClientOptions.credentials.secretAccessKey,
+        sessionToken: s3ClientOptions.credentials.sessionToken,
+        uploadId,
+        partNumber,
+        bucketName,
+        Key,
+        Region: s3ClientOptions.region,
+        expires: 900,
+      })
+    const sdkResult =
+      new URL(
+        await getSignedUrl(client, new UploadPartCommand({
+          Bucket: bucketName,
+          UploadId: uploadId,
+          PartNumber: partNumber,
+          Key,
+        }), { expiresIn: 900 }
+      )
     )
+    assert.strictEqual(implResult.pathname, sdkResult.pathname)
+
+    const extractUploadIdQueryValue = (result) =>
+      result.search.match(/uploadId=(.+?)(&|$)/)[1]
+    assert.strictEqual(extractUploadIdQueryValue(implResult), extractUploadIdQueryValue(sdkResult))
   })
 })