diff --git a/packages/babel-plugin-transform-typescript/src/index.js b/packages/babel-plugin-transform-typescript/src/index.js
index 149c7f1050..b558447733 100644
--- a/packages/babel-plugin-transform-typescript/src/index.js
+++ b/packages/babel-plugin-transform-typescript/src/index.js
@@ -137,7 +137,6 @@ export default declare((api, { jsxPragma = "React" }) => {
           path.remove();
           return;
         }
-        if (node.abstract) node.abstract = null;
       },
 
       Class(path) {
@@ -146,6 +145,7 @@ export default declare((api, { jsxPragma = "React" }) => {
         if (node.typeParameters) node.typeParameters = null;
         if (node.superTypeParameters) node.superTypeParameters = null;
         if (node.implements) node.implements = null;
+        if (node.abstract) node.abstract = null;
 
         // Similar to the logic in `transform-flow-strip-types`, we need to
         // handle `TSParameterProperty` and `ClassProperty` here because the
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-method/input.mjs b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-method/input.mjs
new file mode 100644
index 0000000000..c004b41cd8
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-method/input.mjs
@@ -0,0 +1,5 @@
+import { computed } from 'mobx';
+
+abstract class Foo {
+  @computed get id() {}
+}
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-method/options.json b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-method/options.json
new file mode 100644
index 0000000000..cd0f911709
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-method/options.json
@@ -0,0 +1,11 @@
+{
+  "plugins": [
+    "transform-typescript",
+    [
+      "proposal-decorators",
+      {
+        "legacy": true
+      }
+    ]
+  ]
+}
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-method/output.mjs b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-method/output.mjs
new file mode 100644
index 0000000000..e3ef6d9da4
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-method/output.mjs
@@ -0,0 +1,9 @@
+var _class;
+
+function _applyDecoratedDescriptor(target, property, decorators, descriptor, context) { var desc = {}; Object['ke' + 'ys'](descriptor).forEach(function (key) { desc[key] = descriptor[key]; }); desc.enumerable = !!desc.enumerable; desc.configurable = !!desc.configurable; if ('value' in desc || desc.initializer) { desc.writable = true; } desc = decorators.slice().reverse().reduce(function (desc, decorator) { return decorator(target, property, desc) || desc; }, desc); if (context && desc.initializer !== void 0) { desc.value = desc.initializer ? desc.initializer.call(context) : void 0; desc.initializer = undefined; } if (desc.initializer === void 0) { Object['define' + 'Property'](target, property, desc); desc = null; } return desc; }
+
+import { computed } from 'mobx';
+let Foo = (_class = class Foo {
+  get id() {}
+
+}, (_applyDecoratedDescriptor(_class.prototype, "id", [computed], Object.getOwnPropertyDescriptor(_class.prototype, "id"), _class.prototype)), _class);
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-parameter/input.mjs b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-parameter/input.mjs
new file mode 100644
index 0000000000..d210c98e46
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-parameter/input.mjs
@@ -0,0 +1,5 @@
+import { observable } from 'mobx';
+
+abstract class Foo {
+  @observable id = null;
+}
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-parameter/options.json b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-parameter/options.json
new file mode 100644
index 0000000000..cd0f911709
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-parameter/options.json
@@ -0,0 +1,11 @@
+{
+  "plugins": [
+    "transform-typescript",
+    [
+      "proposal-decorators",
+      {
+        "legacy": true
+      }
+    ]
+  ]
+}
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-parameter/output.mjs b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-parameter/output.mjs
new file mode 100644
index 0000000000..f595936988
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated-parameter/output.mjs
@@ -0,0 +1,17 @@
+var _class, _descriptor;
+
+function _applyDecoratedDescriptor(target, property, decorators, descriptor, context) { var desc = {}; Object['ke' + 'ys'](descriptor).forEach(function (key) { desc[key] = descriptor[key]; }); desc.enumerable = !!desc.enumerable; desc.configurable = !!desc.configurable; if ('value' in desc || desc.initializer) { desc.writable = true; } desc = decorators.slice().reverse().reduce(function (desc, decorator) { return decorator(target, property, desc) || desc; }, desc); if (context && desc.initializer !== void 0) { desc.value = desc.initializer ? desc.initializer.call(context) : void 0; desc.initializer = undefined; } if (desc.initializer === void 0) { Object['define' + 'Property'](target, property, desc); desc = null; } return desc; }
+
+function _initializerWarningHelper(descriptor, context) { throw new Error('Decorating class property failed. Please ensure that ' + 'proposal-class-properties is enabled and set to use loose mode. ' + 'To use proposal-class-properties in spec mode with decorators, wait for ' + 'the next major version of decorators in stage 2.'); }
+
+import { observable } from 'mobx';
+let Foo = (_class = class Foo {
+  id = _initializerWarningHelper(_descriptor, this);
+}, (_descriptor = _applyDecoratedDescriptor(_class.prototype, "id", [observable], {
+  configurable: true,
+  enumerable: true,
+  writable: true,
+  initializer: function () {
+    return null;
+  }
+})), _class);
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated/input.mjs b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated/input.mjs
new file mode 100644
index 0000000000..d1c59625af
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated/input.mjs
@@ -0,0 +1,4 @@
+import { observer } from 'mobx-react';
+
+@observer
+abstract class Foo {}
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated/options.json b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated/options.json
new file mode 100644
index 0000000000..cd0f911709
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated/options.json
@@ -0,0 +1,11 @@
+{
+  "plugins": [
+    "transform-typescript",
+    [
+      "proposal-decorators",
+      {
+        "legacy": true
+      }
+    ]
+  ]
+}
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated/output.mjs b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated/output.mjs
new file mode 100644
index 0000000000..7c0e001398
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/class/abstract-class-decorated/output.mjs
@@ -0,0 +1,5 @@
+var _class;
+
+import { observer } from 'mobx-react';
+
+let Foo = observer(_class = class Foo {}) || _class;