diff --git a/packages/cli/package.json b/packages/cli/package.json
index 27775be15..7f4689f80 100644
--- a/packages/cli/package.json
+++ b/packages/cli/package.json
@@ -66,6 +66,7 @@
     "react-native": "^0.60.0"
   },
   "devDependencies": {
+    "@types/command-exists": "^1.2.0",
     "@types/graceful-fs": "^4.1.3",
     "@types/semver": "^6.0.2",
     "slash": "^3.0.0",
diff --git a/packages/cli/src/commands/doctor/checkInstallation.js b/packages/cli/src/commands/doctor/checkInstallation.ts
similarity index 62%
rename from packages/cli/src/commands/doctor/checkInstallation.js
rename to packages/cli/src/commands/doctor/checkInstallation.ts
index 03e329dc5..cbcd83866 100644
--- a/packages/cli/src/commands/doctor/checkInstallation.js
+++ b/packages/cli/src/commands/doctor/checkInstallation.ts
@@ -1,4 +1,3 @@
-// @flow
 import semver from 'semver';
 import commandExists from 'command-exists';
 
@@ -21,11 +20,16 @@ const doesSoftwareNeedToBeFixed = ({
   version,
   versionRange,
 }: {
-  version: string,
-  versionRange: string,
-}) =>
-  (version === 'Not Found' ||
-    !semver.satisfies(semver.coerce(version), versionRange)) &&
-  `version ${versionRange} is required`;
+  version: string;
+  versionRange: string;
+}) => {
+  const coercedVersion = semver.coerce(version);
+  return (
+    (version === 'Not Found' ||
+      coercedVersion === null ||
+      !semver.satisfies(coercedVersion, versionRange)) &&
+    `version ${versionRange} is required`
+  );
+};
 
 export {PACKAGE_MANAGERS, checkSoftwareInstalled, doesSoftwareNeedToBeFixed};
diff --git a/packages/cli/src/commands/doctor/doctor.js b/packages/cli/src/commands/doctor/doctor.js
index b8a56bcd7..f310f8cac 100644
--- a/packages/cli/src/commands/doctor/doctor.js
+++ b/packages/cli/src/commands/doctor/doctor.js
@@ -5,6 +5,7 @@ import {logger} from '@react-native-community/cli-tools';
 import {getHealthchecks, HEALTHCHECK_TYPES} from './healthchecks';
 // $FlowFixMe - converted to TS
 import {getLoader} from '../../tools/loader';
+// $FlowFixMe - converted to TS
 import printFixOptions, {KEYS} from './printFixOptions';
 import runAutomaticFix, {AUTOMATIC_FIX_LEVELS} from './runAutomaticFix';
 import type {ConfigT} from 'types';
diff --git a/packages/cli/src/commands/doctor/healthchecks/androidHomeEnvVariable.js b/packages/cli/src/commands/doctor/healthchecks/androidHomeEnvVariable.js
index d3422d864..2135ced6b 100644
--- a/packages/cli/src/commands/doctor/healthchecks/androidHomeEnvVariable.js
+++ b/packages/cli/src/commands/doctor/healthchecks/androidHomeEnvVariable.js
@@ -1,6 +1,7 @@
 // @flow
 import chalk from 'chalk';
 import Ora from 'ora';
+// $FlowFixMe - converted to TS
 import {logManualInstallation} from './common';
 import type {HealthCheckInterface} from '../types';
 
diff --git a/packages/cli/src/commands/doctor/healthchecks/androidNDK.js b/packages/cli/src/commands/doctor/healthchecks/androidNDK.js
index d3481e1fe..3550d1aa3 100644
--- a/packages/cli/src/commands/doctor/healthchecks/androidNDK.js
+++ b/packages/cli/src/commands/doctor/healthchecks/androidNDK.js
@@ -1,8 +1,11 @@
 // @flow
 import chalk from 'chalk';
 import Ora from 'ora';
+// $FlowFixMe - converted to TS
 import {logManualInstallation} from './common';
+// $FlowFixMe - converted to TS
 import versionRanges from '../versionRanges';
+// $FlowFixMe - converted to TS
 import {doesSoftwareNeedToBeFixed} from '../checkInstallation';
 import type {EnvironmentInfo, HealthCheckInterface} from '../types';
 
diff --git a/packages/cli/src/commands/doctor/healthchecks/androidSDK.js b/packages/cli/src/commands/doctor/healthchecks/androidSDK.js
index e3a464c60..947b3c9c9 100644
--- a/packages/cli/src/commands/doctor/healthchecks/androidSDK.js
+++ b/packages/cli/src/commands/doctor/healthchecks/androidSDK.js
@@ -1,8 +1,11 @@
 // @flow
 import chalk from 'chalk';
 import Ora from 'ora';
+// $FlowFixMe - converted to TS
 import {logManualInstallation} from './common';
+// $FlowFixMe - converted to TS
 import versionRanges from '../versionRanges';
+// $FlowFixMe - converted to TS
 import {doesSoftwareNeedToBeFixed} from '../checkInstallation';
 import execa from 'execa';
 import type {EnvironmentInfo, HealthCheckInterface} from '../types';
diff --git a/packages/cli/src/commands/doctor/healthchecks/cocoaPods.js b/packages/cli/src/commands/doctor/healthchecks/cocoaPods.js
index 77b8ceadb..92874f0c1 100644
--- a/packages/cli/src/commands/doctor/healthchecks/cocoaPods.js
+++ b/packages/cli/src/commands/doctor/healthchecks/cocoaPods.js
@@ -1,4 +1,5 @@
 // @flow
+// $FlowFixMe - converted to TS
 import {checkSoftwareInstalled} from '../checkInstallation';
 // $FlowFixMe - converted to TS
 import {installCocoaPods} from '../../../tools/installPods';
diff --git a/packages/cli/src/commands/doctor/healthchecks/common.js b/packages/cli/src/commands/doctor/healthchecks/common.ts
similarity index 80%
rename from packages/cli/src/commands/doctor/healthchecks/common.js
rename to packages/cli/src/commands/doctor/healthchecks/common.ts
index 11d0008c6..e90662857 100644
--- a/packages/cli/src/commands/doctor/healthchecks/common.js
+++ b/packages/cli/src/commands/doctor/healthchecks/common.ts
@@ -1,9 +1,8 @@
-// @flow
 import {logger} from '@react-native-community/cli-tools';
 import chalk from 'chalk';
 
 // Space is necessary to keep correct ordering on screen
-const logMessage = message => logger.log(`   ${message}`);
+const logMessage = (message: string) => logger.log(`   ${message}`);
 
 const logManualInstallation = ({
   healthcheck = '',
@@ -11,10 +10,10 @@ const logManualInstallation = ({
   command,
   message,
 }: {
-  healthcheck?: string,
-  url?: string,
-  command?: string,
-  message?: string,
+  healthcheck?: string;
+  url?: string;
+  command?: string;
+  message?: string;
 }) => {
   if (message) {
     return logMessage(message);
diff --git a/packages/cli/src/commands/doctor/healthchecks/iosDeploy.js b/packages/cli/src/commands/doctor/healthchecks/iosDeploy.js
index c5639c1b4..90498b332 100644
--- a/packages/cli/src/commands/doctor/healthchecks/iosDeploy.js
+++ b/packages/cli/src/commands/doctor/healthchecks/iosDeploy.js
@@ -1,8 +1,10 @@
 // @flow
 import execa from 'execa';
 import Ora from 'ora';
+// $FlowFixMe - converted to TS
 import {checkSoftwareInstalled, PACKAGE_MANAGERS} from '../checkInstallation';
 import {packageManager} from './packageManagers';
+// $FlowFixMe - converted to TS
 import {logManualInstallation} from './common';
 import type {HealthCheckInterface} from '../types';
 
diff --git a/packages/cli/src/commands/doctor/healthchecks/nodeJS.js b/packages/cli/src/commands/doctor/healthchecks/nodeJS.js
index a4dfdd8eb..ce0a4b91a 100644
--- a/packages/cli/src/commands/doctor/healthchecks/nodeJS.js
+++ b/packages/cli/src/commands/doctor/healthchecks/nodeJS.js
@@ -1,7 +1,10 @@
 // @flow
 import Ora from 'ora';
+// $FlowFixMe - converted to TS
 import versionRanges from '../versionRanges';
+// $FlowFixMe - converted to TS
 import {doesSoftwareNeedToBeFixed} from '../checkInstallation';
+// $FlowFixMe - converted to TS
 import {logManualInstallation} from './common';
 import type {EnvironmentInfo, HealthCheckInterface} from '../types';
 
diff --git a/packages/cli/src/commands/doctor/healthchecks/packageManagers.js b/packages/cli/src/commands/doctor/healthchecks/packageManagers.js
index 0ffb26c79..f2e369b4b 100644
--- a/packages/cli/src/commands/doctor/healthchecks/packageManagers.js
+++ b/packages/cli/src/commands/doctor/healthchecks/packageManagers.js
@@ -1,10 +1,12 @@
 // @flow
 import fs from 'fs';
 import Ora from 'ora';
+// $FlowFixMe - converted to TS
 import versionRanges from '../versionRanges';
 import {
   PACKAGE_MANAGERS,
   doesSoftwareNeedToBeFixed,
+  // $FlowFixMe - converted to TS
 } from '../checkInstallation';
 // $FlowFixMe - converted to TS
 import {install} from '../../../tools/install';
diff --git a/packages/cli/src/commands/doctor/healthchecks/watchman.js b/packages/cli/src/commands/doctor/healthchecks/watchman.js
index 2b392f9c4..4706b6746 100644
--- a/packages/cli/src/commands/doctor/healthchecks/watchman.js
+++ b/packages/cli/src/commands/doctor/healthchecks/watchman.js
@@ -1,6 +1,8 @@
 // @flow
 import Ora from 'ora';
+// $FlowFixMe - converted to TS
 import versionRanges from '../versionRanges';
+// $FlowFixMe - converted to TS
 import {doesSoftwareNeedToBeFixed} from '../checkInstallation';
 // $FlowFixMe - converted to TS
 import {install} from '../../../tools/install';
diff --git a/packages/cli/src/commands/doctor/healthchecks/xcode.js b/packages/cli/src/commands/doctor/healthchecks/xcode.js
index 74ac04a7c..dffd1e408 100644
--- a/packages/cli/src/commands/doctor/healthchecks/xcode.js
+++ b/packages/cli/src/commands/doctor/healthchecks/xcode.js
@@ -1,7 +1,10 @@
 // @flow
 import Ora from 'ora';
+// $FlowFixMe - converted to TS
 import versionRanges from '../versionRanges';
+// $FlowFixMe - converted to TS
 import {doesSoftwareNeedToBeFixed} from '../checkInstallation';
+// $FlowFixMe - converted to TS
 import {logManualInstallation} from './common';
 import type {EnvironmentInfo, HealthCheckInterface} from '../types';
 
diff --git a/packages/cli/src/commands/doctor/printFixOptions.js b/packages/cli/src/commands/doctor/printFixOptions.ts
similarity index 78%
rename from packages/cli/src/commands/doctor/printFixOptions.js
rename to packages/cli/src/commands/doctor/printFixOptions.ts
index 9134f8c0f..7902ded79 100644
--- a/packages/cli/src/commands/doctor/printFixOptions.js
+++ b/packages/cli/src/commands/doctor/printFixOptions.ts
@@ -1,4 +1,3 @@
-// @flow
 import chalk from 'chalk';
 import {logger} from '@react-native-community/cli-tools';
 
@@ -9,7 +8,7 @@ const KEYS = {
   EXIT: '\r',
 };
 
-const printOption = option => logger.log(` \u203A ${option}`);
+const printOption = (option: string) => logger.log(` \u203A ${option}`);
 const printOptions = () => {
   logger.log();
   logger.log(chalk.bold('Usage'));
@@ -30,11 +29,12 @@ const printOptions = () => {
 };
 
 export {KEYS};
-export default ({onKeyPress}: {onKeyPress: any}) => {
+export default ({onKeyPress}: {onKeyPress: (...args: any[]) => void}) => {
   printOptions();
 
-  // $FlowFixMe
-  process.stdin.setRawMode(true);
+  if (process.stdin.setRawMode) {
+    process.stdin.setRawMode(true);
+  }
   process.stdin.resume();
   process.stdin.setEncoding('utf8');
   process.stdin.on('data', onKeyPress);
diff --git a/packages/cli/src/commands/doctor/types.ts b/packages/cli/src/commands/doctor/types.ts
new file mode 100644
index 000000000..9c5a5e7a8
--- /dev/null
+++ b/packages/cli/src/commands/doctor/types.ts
@@ -0,0 +1,78 @@
+import Ora from 'ora';
+
+export type EnvironmentInfo = {
+  System: {
+    OS: string;
+    CPU: string;
+    Memory: string;
+    Shell: {
+      version: string;
+      path: string;
+    };
+  };
+  Binaries: {
+    Node: {
+      version: string;
+      path: string;
+    };
+    Yarn: {
+      version: string;
+      path: string;
+    };
+    npm: {
+      version: string;
+      path: string;
+    };
+    Watchman: {
+      version: string;
+      path: string;
+    };
+  };
+  SDKs: {
+    'iOS SDK': {
+      Platforms: string[];
+    };
+    'Android SDK': {
+      'API Levels': string[];
+      'Build Tools': string[];
+      'System Images': string[];
+      'Android NDK': string;
+    };
+  };
+  IDEs: {
+    'Android Studio': string;
+    Emacs: {
+      version: string;
+      path: string;
+    };
+    Nano: {
+      version: string;
+      path: string;
+    };
+    VSCode: {
+      version: string;
+      path: string;
+    };
+    Vim: {
+      version: string;
+      path: string;
+    };
+    Xcode: {
+      version: string;
+      path: string;
+    };
+  };
+};
+
+export type HealthCheckInterface = {
+  label: string;
+  visible?: boolean | void;
+  isRequired?: boolean;
+  getDiagnostics: (
+    environmentInfo: EnvironmentInfo,
+  ) => Promise<{version?: string; needsToBeFixed: boolean | string}>;
+  runAutomaticFix: (args: {
+    loader: typeof Ora;
+    environmentInfo: EnvironmentInfo;
+  }) => Promise<void> | void;
+};
diff --git a/packages/cli/src/commands/doctor/versionRanges.js b/packages/cli/src/commands/doctor/versionRanges.ts
similarity index 95%
rename from packages/cli/src/commands/doctor/versionRanges.js
rename to packages/cli/src/commands/doctor/versionRanges.ts
index d1909f150..d67496bd6 100644
--- a/packages/cli/src/commands/doctor/versionRanges.js
+++ b/packages/cli/src/commands/doctor/versionRanges.ts
@@ -1,4 +1,3 @@
-// @flow
 export default {
   // Common
   NODE_JS: '>= 8.3',
diff --git a/yarn.lock b/yarn.lock
index 3dc75009c..c33e45351 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2027,6 +2027,11 @@
   dependencies:
     "@babel/types" "^7.3.0"
 
+"@types/command-exists@^1.2.0":
+  version "1.2.0"
+  resolved "https://registry.yarnpkg.com/@types/command-exists/-/command-exists-1.2.0.tgz#d97e0ed10097090e4ab0367ed425b0312fad86f3"
+  integrity sha512-ugsxEJfsCuqMLSuCD4PIJkp5Uk2z6TCMRCgYVuhRo5cYQY3+1xXTQkSlPtkpGHuvWMjS2KTeVQXxkXRACMbM6A==
+
 "@types/events@*":
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/@types/events/-/events-3.0.0.tgz#2862f3f58a9a7f7c3e78d79f130dd4d71c25c2a7"