diff --git a/.changeset/twenty-ravens-attend.md b/.changeset/twenty-ravens-attend.md
new file mode 100644
index 000000000000..e3e46aa2f226
--- /dev/null
+++ b/.changeset/twenty-ravens-attend.md
@@ -0,0 +1,8 @@
+---
+"@typescript/vfs": patch
+"@typescript/twoslash": patch
+"@typescript/sandbox": patch
+"@typescript/ata": patch
+---
+
+Handle `.d.cts` and `.d.mts` files
diff --git a/packages/ata/src/index.ts b/packages/ata/src/index.ts
index 0f0070501be6..f52d3dcb04f8 100644
--- a/packages/ata/src/index.ts
+++ b/packages/ata/src/index.ts
@@ -71,7 +71,7 @@ export const setupTypeAcquisition = (config: ATABootstrapConfig) => {
     const treesOnly = trees.filter(t => !("error" in t)) as NPMTreeMeta[]
 
     // These are the modules which we can grab directly
-    const hasDTS = treesOnly.filter(t => t.files.find(f => f.name.endsWith(".d.ts")))
+    const hasDTS = treesOnly.filter(t => t.files.find(f => isDtsFile(f.name)))
     const dtsFilesFromNPM = hasDTS.map(t => treeToDTSFiles(t, `/node_modules/${t.moduleName}`))
 
     // These are ones we need to look on DT for (which may not be there, who knows)
@@ -142,7 +142,7 @@ function treeToDTSFiles(tree: NPMTreeMeta, vfsPrefix: string) {
   const dtsRefs: ATADownload[] = []
 
   for (const file of tree.files) {
-    if (file.name.endsWith(".d.ts")) {
+    if (isDtsFile(file.name)) {
       dtsRefs.push({
         moduleName: tree.moduleName,
         moduleVersion: tree.version,
@@ -170,7 +170,7 @@ export const getReferencesForModule = (ts: typeof import("typescript"), code: st
   const references = meta.referencedFiles
     .concat(meta.importedFiles)
     .concat(meta.libReferenceDirectives)
-    .filter(f => !f.fileName.endsWith(".d.ts"))
+    .filter(f => !isDtsFile(f.fileName))
     .filter(d => !libMap.has(d.fileName))
 
   return references.map(r => {
@@ -268,3 +268,7 @@ function getDTName(s: string) {
   }
   return s
 }
+
+function isDtsFile(file: string) {
+  return /\.d\.([^\.]+\.)?[cm]?ts$/i.test(file)
+}
diff --git a/packages/sandbox/src/index.ts b/packages/sandbox/src/index.ts
index fbb647ba8429..b60c9ad5114f 100644
--- a/packages/sandbox/src/index.ts
+++ b/packages/sandbox/src/index.ts
@@ -318,12 +318,15 @@ export const createTypeScriptSandbox = (
     return (firstJS && firstJS.text) || ""
   }
 
+  const isDtsFile = (name: string) => /\.d\.([^\.]+\.)?[cm]?ts$/i.test(name)
+
   /** Gets the DTS for the JS/TS  of compiling your editor's code */
   const getDTSForCode = async () => {
     const result = await getEmitResult(/*emitOnlyDtsFiles*/ undefined, /*forceDtsEmit*/ true)
-    return result.outputFiles.find((o: any) => o.name.endsWith(".d.ts"))?.text || ""
+    return result.outputFiles.find((o: any) => isDtsFile(o.name))?.text || ""
   }
 
+
   const getWorkerProcess = async (): Promise<TypeScriptWorker> => {
     const worker = await getWorker()
     // @ts-ignore
diff --git a/packages/ts-twoslasher/src/index.ts b/packages/ts-twoslasher/src/index.ts
index c377237de5ea..0864bf3de185 100755
--- a/packages/ts-twoslasher/src/index.ts
+++ b/packages/ts-twoslasher/src/index.ts
@@ -742,7 +742,7 @@ export function twoslasher(code: string, extension: string, options: TwoSlashOpt
     // Get the file which created the file we want to show:
     const emitFilename = handbookOptions.showEmittedFile || defaultFileName
     const emitSourceFilename =
-      fsRoot + emitFilename.replace(".jsx", "").replace(".js", "").replace(".d.ts", "").replace(".map", "")
+      fsRoot + emitFilename.replace(".jsx", "").replace(".js", "").replace(/\.d\.([^\.]+\.)?[cm]?ts$/i, "").replace(".map", "")
 
     let emitSource = filenames.find(f => f === emitSourceFilename + ".ts" || f === emitSourceFilename + ".tsx")
 
diff --git a/packages/typescript-vfs/src/index.ts b/packages/typescript-vfs/src/index.ts
index 10ec61f02026..9827a3b528d2 100755
--- a/packages/typescript-vfs/src/index.ts
+++ b/packages/typescript-vfs/src/index.ts
@@ -241,8 +241,10 @@ export const createDefaultMapFromNodeModules = (
     return fs.readFileSync(path.join(lib, name), "utf8")
   }
 
+  const isDtsFile = (file: string) => /\.d\.([^\.]+\.)?[cm]?ts$/i.test(file)
+
   const libFiles = fs.readdirSync(tsLibDirectory || path.dirname(require.resolve("typescript")))
-  const knownLibFiles = libFiles.filter(f => f.startsWith("lib.") && f.endsWith(".d.ts"))
+  const knownLibFiles = libFiles.filter(f => f.startsWith("lib.") && isDtsFile(f))
 
   const fsMap = new Map<string, string>()
   knownLibFiles.forEach(lib => {