diff --git a/src/collector/declarations.js b/src/collector/declarations.js
index 6475201..77460a1 100644
--- a/src/collector/declarations.js
+++ b/src/collector/declarations.js
@@ -5,13 +5,14 @@ import type {
     Block, ClassDeclaration, ExportDefaultDeclaration, ExportNamedDeclaration, Identifier,
     ImportDeclaration, ImportDefaultSpecifier, ImportSpecifier, InterfaceDeclaration,
     Node, TypeAlias, TypeParameterDeclaration, VariableDeclaration, VariableDeclarator,
+    DeclareTypeAlias, DeclareInterface, DeclareClass,
 } from '@babel/types';
 
 import {
-    isCallExpression, isClassDeclaration, isClassMethod, isExportDefaultDeclaration,
+    isCallExpression, isClassDeclaration, isClassMethod, isExportDefaultDeclaration, isProgram,
     isExportNamedDeclaration, isIdentifier, isImportDeclaration, isImportNamespaceSpecifier,
-    isImportSpecifier, isInterfaceDeclaration, isObjectPattern, isObjectProperty, isProgram,
-    isStringLiteral, isTypeAlias, isVariableDeclaration,
+    isImportSpecifier, isInterfaceDeclaration, isObjectPattern, isObjectProperty, isDeclareClass,
+    isStringLiteral, isTypeAlias, isVariableDeclaration, isDeclareTypeAlias, isDeclareInterface,
 } from '@babel/types';
 
 import {invariant} from '../utils';
@@ -194,10 +195,12 @@ function processExportDefaultDeclaration(ctx: Context, node: ExportDefaultDeclar
  * TODO: support "declare ..." form.
  */
 
-type Declaration = TypeAlias | InterfaceDeclaration | ClassDeclaration;
+type Declaration = TypeAlias | InterfaceDeclaration | ClassDeclaration
+                 | DeclareTypeAlias | DeclareInterface | DeclareClass;
 
 function isDeclaration(node: mixed): boolean %checks {
-    return isTypeAlias(node) || isInterfaceDeclaration(node) || isClassDeclaration(node);
+    return isTypeAlias(node) || isInterfaceDeclaration(node) || isClassDeclaration(node)
+        || isDeclareTypeAlias(node) || isDeclareInterface(node) || isDeclareClass(node);
 }
 
 function processDeclaration(ctx: Context, node: Declaration) {
diff --git a/src/collector/definitions.js b/src/collector/definitions.js
index 0a2f1a5..2bd7be1 100644
--- a/src/collector/definitions.js
+++ b/src/collector/definitions.js
@@ -6,7 +6,7 @@ import type {
     GenericTypeAnnotation, InterfaceDeclaration, IntersectionTypeAnnotation, TypeAlias,
     UnionTypeAnnotation, NullableTypeAnnotation, ObjectTypeIndexer, ObjectTypeProperty,
     StringLiteralTypeAnnotation, ObjectTypeAnnotation, AnyTypeAnnotation, MixedTypeAnnotation,
-    TupleTypeAnnotation,
+    TupleTypeAnnotation, DeclareTypeAlias, DeclareInterface, DeclareClass,
 } from '@babel/types';
 
 import {
@@ -26,7 +26,7 @@ import {extractPragmas} from './pragmas';
 
 import {invariant} from '../utils';
 
-function processTypeAlias(ctx: Context, node: TypeAlias) {
+function processTypeAlias(ctx: Context, node: TypeAlias | DeclareTypeAlias) {
     const {name} = node.id;
     const type = makeType(ctx, node.right);
 
@@ -37,7 +37,10 @@ function processTypeAlias(ctx: Context, node: TypeAlias) {
 }
 
 // TODO: type params.
-function processInterfaceDeclaration(ctx: Context, node: InterfaceDeclaration) {
+function processInterfaceDeclaration(
+    ctx: Context,
+    node: InterfaceDeclaration | DeclareInterface | DeclareClass
+) {
     const {name} = node.id;
     const type = makeType(ctx, node.body);
 
@@ -282,6 +285,9 @@ function makeReference(ctx: Context, node: GenericTypeAnnotation): ?Type {
 
 export default {
     TypeAlias: processTypeAlias,
+    DeclareTypeAlias: processTypeAlias,
     InterfaceDeclaration: processInterfaceDeclaration,
+    DeclareInterface: processInterfaceDeclaration,
     ClassDeclaration: processClassDeclaration,
+    DeclareClass: processInterfaceDeclaration,
 }
diff --git a/tests/samples/declare/source.js b/tests/samples/declare/source.js
new file mode 100644
index 0000000..6ccab48
--- /dev/null
+++ b/tests/samples/declare/source.js
@@ -0,0 +1,13 @@
+declare type Type = {
+    a: string,
+};
+
+declare interface Interface {
+    a: Type;
+};
+
+declare class Class {
+    a: Interface;
+}
+
+export {Type, Interface, Class};
diff --git a/tests/samples/declare/types.yaml b/tests/samples/declare/types.yaml
new file mode 100644
index 0000000..fd1e524
--- /dev/null
+++ b/tests/samples/declare/types.yaml
@@ -0,0 +1,22 @@
+-   kind: record
+    fields:
+    -   name: a
+        value: {kind: string}
+        required: true
+    id: [declare, Type]
+-   kind: record
+    fields:
+    -   name: a
+        value:
+            kind: reference
+            to: [declare, Type]
+        required: true
+    id: [declare, Interface]
+-   kind: record
+    fields:
+    -   name: a
+        value:
+            kind: reference
+            to: [declare, Interface]
+        required: true
+    id: [declare, Class]