diff --git a/index.js b/index.js
index f322dfc..e796b89 100644
--- a/index.js
+++ b/index.js
@@ -3,12 +3,32 @@ const fs = require('fs')
 const path = require('path')
 const { promisify } = require('util')
 
-function escapeNewlines (str) {
-  return str.replace(/\n/g, '\\n')
+function escapeCharacters (str) {
+  let wrapper = ''
+
+  // If the string contains a space or dollar sign, wrap it in single quotes.
+  if (str.match(/[\s$]/)) {
+    wrapper = '\''
+  }
+
+  // If the string contains a newline, escape it and wrap in double quotes.
+  // Also escape any dollar signs to prevent interpolation.
+  if (str.match(/\n/)) {
+    str = str.replace(/\$/g, '\\$').replace(/\n/g, '\\n')
+    wrapper = '"'
+  }
+
+  // If we're wrapping the string, escape any wrapper characters.
+  if (wrapper !== '') {
+    str = str.replace(new RegExp(wrapper, 'g'), `\\${wrapper}`)
+  }
+
+  // Wrap the string (if necessary) and return it.
+  return [wrapper, str, wrapper].join('')
 }
 
 function format (key, value) {
-  return `${key}=${escapeNewlines(value)}`
+  return `${key}=${escapeCharacters(value)}`
 }
 
 module.exports = async function updateDotenv (env) {
diff --git a/index.test.js b/index.test.js
index 2b79811..c124524 100644
--- a/index.test.js
+++ b/index.test.js
@@ -25,7 +25,7 @@ describe('update-dotenv', () => {
 
   test('properly writes multi-line strings', async () => {
     await updateDotenv({ FOO: 'bar\nbaz' })
-    expect(fs.readFileSync('.env', 'UTF-8')).toEqual('FOO=bar\\nbaz')
+    expect(fs.readFileSync('.env', 'UTF-8')).toEqual('FOO="bar\\nbaz"')
   })
 
   test('appends new variables to existing variables', async () => {
@@ -33,4 +33,24 @@ describe('update-dotenv', () => {
     await updateDotenv({ SECOND: 'bar' })
     expect(fs.readFileSync('.env', 'UTF-8')).toEqual('FIRST=foo\nSECOND=bar')
   })
+
+  test('wraps strings with spaces in quotes', async () => {
+    await updateDotenv({ FOO: 'foo bar' })
+    expect(fs.readFileSync('.env', 'UTF-8')).toEqual('FOO=\'foo bar\'')
+  })
+
+  test('wraps strings with dollar signs in quotes', async () => {
+    await updateDotenv({ FOO: '$foo $bar' })
+    expect(fs.readFileSync('.env', 'UTF-8')).toEqual('FOO=\'$foo $bar\'')
+  })
+
+  test('escapes single quotes', async () => {
+    await updateDotenv({ FOO: '\'foo\' "$and" \'bar\'' })
+    expect(fs.readFileSync('.env', 'UTF-8')).toEqual('FOO=\'\\\'foo\\\' "$and" \\\'bar\\\'\'')
+  })
+
+  test('escapes double quotes', async () => {
+    await updateDotenv({ FOO: "\"foo\"\n'$and'\n\"bar\"" })
+    expect(fs.readFileSync('.env', 'UTF-8')).toEqual('FOO="\\"foo\\"\\n\'\\$and\'\\n\\"bar\\""')
+  })
 })