diff --git a/lib/node-modules-paths.js b/lib/node-modules-paths.js
index 7c58e106..8888117d 100644
--- a/lib/node-modules-paths.js
+++ b/lib/node-modules-paths.js
@@ -20,6 +20,8 @@ module.exports = function (start, opts) {
     var parts = start.split(splitRe);
 
     var dirs = [];
+    var envDirs = [];
+    var envDelimeter = ':';
     for (var i = parts.length - 1; i >= 0; i--) {
         if (modules.indexOf(parts[i]) !== -1) continue;
         dirs = dirs.concat(modules.map(function(module_dir) {
@@ -31,6 +33,10 @@ module.exports = function (start, opts) {
     }
     if (process.platform === 'win32'){
         dirs[dirs.length-1] = dirs[dirs.length-1].replace(":", ":\\");
+        envDelimeter = ';';
     }
-    return dirs.concat(opts.paths);
+    if (process.env.NODE_PATH) {
+        envDirs = process.env.NODE_PATH.split(envDelimeter);
+    }
+    return dirs.concat(opts.paths, envDirs);
 }
diff --git a/test/node_path.js b/test/node_path.js
index 1472bdb7..7b1f8a06 100644
--- a/test/node_path.js
+++ b/test/node_path.js
@@ -2,9 +2,10 @@ var path = require('path');
 var test = require('tap').test;
 var resolve = require('../');
 
-test('$NODE_PATH', function (t) {
-    t.plan(3);
-    
+// Ensure that the `opts.paths` paths are searched
+test('opts.paths', function (t) {
+    t.plan(4);
+
     resolve('aaa', {
         paths: [
             __dirname + '/node_path/x',
@@ -14,7 +15,7 @@ test('$NODE_PATH', function (t) {
     }, function (err, res) {
         t.equal(res, __dirname + '/node_path/x/aaa/index.js');
     });
-    
+
     resolve('bbb', {
         paths: [
             __dirname + '/node_path/x',
@@ -24,7 +25,7 @@ test('$NODE_PATH', function (t) {
     }, function (err, res) {
         t.equal(res, __dirname + '/node_path/y/bbb/index.js');
     });
-    
+
     resolve('ccc', {
         paths: [
             __dirname + '/node_path/x',
@@ -46,3 +47,71 @@ test('$NODE_PATH', function (t) {
         t.equal(res, path.resolve(__dirname, '..', 'node_modules/tap/lib/main.js'));
     });
 });
+
+// Ensure that the `NODE_PATH` environment is searched
+test('$NODE_PATH async', function (t) {
+    t.plan(4);
+
+    // Construct the NODE_PATH environment variable
+    var nodePaths = [
+        __dirname + '/node_path/x',
+        __dirname + '/node_path/y'
+    ];
+
+    var delimeter = process.platform === 'win32' ? ';' : ':';
+    process.env.NODE_PATH = nodePaths.join(delimeter);
+
+    resolve('aaa', {
+    }, function (err, res) {
+        t.equal(res, __dirname + '/node_path/x/aaa/index.js');
+    });
+
+    resolve('bbb', {
+    }, function (err, res) {
+        t.equal(res, __dirname + '/node_path/y/bbb/index.js');
+    });
+
+    resolve('ccc', {
+    }, function (err, res) {
+        t.equal(res, __dirname + '/node_path/x/ccc/index.js');
+    });
+
+    // ensure that relative paths still resolve against the
+    // regular `node_modules` correctly
+    resolve('tap', {
+        paths: [
+            'node_path',
+        ],
+        basedir: 'node_path/x',
+    }, function (err, res) {
+        t.equal(res, path.resolve(__dirname, '..', 'node_modules/tap/lib/main.js'));
+    });
+});
+
+// Ensure that the `NODE_PATH` environment is searched in sync
+test('$NODE_PATH sync', function (t) {
+    t.plan(4);
+
+    // Construct the NODE_PATH environment variable
+    var nodePaths = [
+        __dirname + '/node_path/x',
+        __dirname + '/node_path/y'
+    ];
+
+    var delimeter = process.platform === 'win32' ? ';' : ':';
+    process.env.NODE_PATH = nodePaths.join(delimeter);
+
+    var res = resolve.sync('aaa');
+    t.equal(res, __dirname + '/node_path/x/aaa/index.js');
+
+    res = resolve.sync('bbb');
+    t.equal(res, __dirname + '/node_path/y/bbb/index.js');
+
+    res = resolve.sync('ccc');
+    t.equal(res, __dirname + '/node_path/x/ccc/index.js');
+
+    // ensure that relative paths still resolve against the
+    // regular `node_modules` correctly
+    res = resolve.sync('tap');
+    t.equal(res, path.resolve(__dirname, '..', 'node_modules/tap/lib/main.js'));
+});