diff --git a/nixos/modules/programs/zsh/oh-my-zsh.nix b/nixos/modules/programs/zsh/oh-my-zsh.nix
index b995d390b279..f4df4e983e42 100644
--- a/nixos/modules/programs/zsh/oh-my-zsh.nix
+++ b/nixos/modules/programs/zsh/oh-my-zsh.nix
@@ -3,7 +3,30 @@
 with lib;
 
 let
+
   cfg = config.programs.zsh.ohMyZsh;
+
+  mkLinkFarmEntry = name: dir:
+    let
+      env = pkgs.buildEnv {
+        name = "zsh-${name}-env";
+        paths = cfg.customPkgs;
+        pathsToLink = "/share/zsh/${dir}";
+      };
+    in
+      { inherit name; path = "${env}/share/zsh/${dir}"; };
+
+  mkLinkFarmEntry' = name: mkLinkFarmEntry name name;
+
+  custom =
+    if cfg.custom != null then cfg.custom
+    else if length cfg.customPkgs == 0 then null
+    else pkgs.linkFarm "oh-my-zsh-custom" [
+      (mkLinkFarmEntry' "themes")
+      (mkLinkFarmEntry "completions" "site-functions")
+      (mkLinkFarmEntry' "plugins")
+    ];
+
 in
   {
     options = {
@@ -34,10 +57,19 @@ in
         };
 
         custom = mkOption {
-          default = "";
-          type = types.str;
+          default = null;
+          type = with types; nullOr str;
           description = ''
             Path to a custom oh-my-zsh package to override config of oh-my-zsh.
+            (Can't be used along with `customPkgs`).
+          '';
+        };
+
+        customPkgs = mkOption {
+          default = [];
+          type = types.listOf types.package;
+          description = ''
+            List of custom packages that should be loaded into `oh-my-zsh`.
           '';
         };
 
@@ -67,7 +99,7 @@ in
 
       environment.systemPackages = [ cfg.package ];
 
-      programs.zsh.interactiveShellInit = with builtins; ''
+      programs.zsh.interactiveShellInit = ''
         # oh-my-zsh configuration generated by NixOS
         export ZSH=${cfg.package}/share/oh-my-zsh
 
@@ -75,8 +107,8 @@ in
           "plugins=(${concatStringsSep " " cfg.plugins})"
         }
 
-        ${optionalString (stringLength(cfg.custom) > 0)
-          "ZSH_CUSTOM=\"${cfg.custom}\""
+        ${optionalString (custom != null)
+          "ZSH_CUSTOM=\"${custom}\""
         }
 
         ${optionalString (stringLength(cfg.theme) > 0)
@@ -92,5 +124,15 @@ in
 
         source $ZSH/oh-my-zsh.sh
       '';
+
+      assertions = [
+        {
+          assertion = cfg.custom != null -> cfg.customPkgs == [];
+          message = "If `cfg.custom` is set for `ZSH_CUSTOM`, `customPkgs` can't be used!";
+        }
+      ];
+
     };
+
+    meta.doc = ./oh-my-zsh.xml;
   }
diff --git a/nixos/modules/programs/zsh/oh-my-zsh.xml b/nixos/modules/programs/zsh/oh-my-zsh.xml
new file mode 100644
index 000000000000..b74da8630ee7
--- /dev/null
+++ b/nixos/modules/programs/zsh/oh-my-zsh.xml
@@ -0,0 +1,125 @@
+<chapter xmlns="http://docbook.org/ns/docbook"
+         xmlns:xlink="http://www.w3.org/1999/xlink"
+         xmlns:xi="http://www.w3.org/2001/XInclude"
+         version="5.0"
+         xml:id="module-programs-zsh-ohmyzsh">
+
+<title>Oh my ZSH</title>
+
+<para><literal><link xlink:href="https://ohmyz.sh/">oh-my-zsh</link></literal> is a framework
+to manage your <link xlink:href="https://www.zsh.org/">ZSH</link> configuration
+including completion scripts for several CLI tools or custom prompt themes.</para>
+
+<section><title>Basic usage</title>
+<para>The module uses the <literal>oh-my-zsh</literal> package with all available features.  The
+initial setup using Nix expressions is fairly similar to the configuration format
+of <literal>oh-my-zsh</literal>.
+
+<programlisting>
+{
+  programs.ohMyZsh = {
+    enable = true;
+    plugins = [ "git" "python" "man" ];
+    theme = "agnoster";
+  };
+}
+</programlisting>
+
+For a detailed explanation of these arguments please refer to the
+<link xlink:href="https://github.com/robbyrussell/oh-my-zsh/wiki"><literal>oh-my-zsh</literal> docs</link>.
+</para>
+<para>The expression generates the needed
+configuration and writes it into your <literal>/etc/zshrc</literal>.
+</para></section>
+
+<section><title>Custom additions</title>
+
+<para>Sometimes third-party or custom scripts such as a modified theme may be needed.
+<literal>oh-my-zsh</literal> provides the
+<link xlink:href="https://github.com/robbyrussell/oh-my-zsh/wiki/Customization#overriding-internals"><literal>ZSH_CUSTOM</literal></link> 
+environment variable for this which points to a directory with additional scripts.</para>
+
+<para>The module can do this as well:
+
+<programlisting>
+{
+  programs.ohMyZsh.custom = "~/path/to/custom/scripts";
+}
+</programlisting>
+</para></section>
+
+<section><title>Custom environments</title>
+
+<para>There are several extensions for <literal>oh-my-zsh</literal> packaged in <literal>nixpkgs</literal>.
+One of them is <link xlink:href="https://github.com/spwhitt/nix-zsh-completions">nix-zsh-completions</link>
+which bundles completion scripts and a plugin for <literal>oh-my-zsh</literal>.</para>
+
+<para>Rather than using a single mutable path for <literal>ZSH_CUSTOM</literal>, it's also possible to
+generate this path from a list of Nix packages:
+
+<programlisting>
+{ pkgs, ... }:
+{
+  programs.ohMyZsh.customPkgs = with pkgs; [
+    pkgs.nix-zsh-completions
+    # and even more...
+  ];
+}
+</programlisting>
+
+Internally a single store path will be created using <literal>buildEnv</literal>.
+Please refer to the docs of
+<link xlink:href="https://nixos.org/nixpkgs/manual/#sec-building-environment"><literal>buildEnv</literal></link>
+for further reference.</para>
+
+<para><emphasis>Please keep in mind that this is not compatible with <literal>programs.ohMyZsh.custom</literal>
+as it requires an immutable store path while <literal>custom</literal> shall remain mutable! An evaluation failure
+will be thrown if both <literal>custom</literal> and <literal>customPkgs</literal> are set.</emphasis>
+</para></section>
+
+<section><title>Package your own customizations</title>
+
+<para>If third-party customizations (e.g. new themes) are supposed to be added to <literal>oh-my-zsh</literal>
+there are several pitfalls to keep in mind:</para>
+
+<itemizedlist>
+  <listitem>
+    <para>To comply with the default structure of <literal>ZSH</literal> the entire output needs to be written to
+    <literal>$out/share/zsh.</literal></para>
+  </listitem>
+  <listitem>
+    <para>Completion scripts are supposed to be stored at <literal>$out/share/zsh/site-functions</literal>. This directory
+    is part of the <literal><link xlink:href="http://zsh.sourceforge.net/Doc/Release/Functions.html">fpath</link></literal>
+    and the package should be compatible with pure <literal>ZSH</literal> setups. The module will automatically link
+    the contents of <literal>site-functions</literal> to completions directory in the proper store path.</para>
+  </listitem>
+  <listitem>
+    <para>The <literal>plugins</literal> directory needs the structure <literal>pluginname/pluginname.plugin.zsh</literal>
+    as structured in the <link xlink:href="https://github.com/robbyrussell/oh-my-zsh/tree/91b771914bc7c43dd7c7a43b586c5de2c225ceb7/plugins">upstream repo.</link>
+    </para>
+  </listitem>
+</itemizedlist>
+
+<para>
+A derivation for <literal>oh-my-zsh</literal> may look like this:
+<programlisting>
+{ stdenv, fetchFromGitHub }:
+
+stdenv.mkDerivation rec {
+  name = "exemplary-zsh-customization-${version}";
+  version = "1.0.0";
+  src = fetchFromGitHub {
+    # path to the upstream repository
+  };
+
+  dontBuild = true;
+  installPhase = ''
+    mkdir -p $out/share/zsh/site-functions
+    cp {themes,plugins} $out/share/zsh
+    cp completions $out/share/zsh/site-functions
+  '';
+}
+</programlisting>
+</para>
+</section>
+</chapter>
diff --git a/pkgs/shells/zsh/lambda-mod-zsh-theme/default.nix b/pkgs/shells/zsh/lambda-mod-zsh-theme/default.nix
index 6dea51a487e9..c4d63bd27710 100644
--- a/pkgs/shells/zsh/lambda-mod-zsh-theme/default.nix
+++ b/pkgs/shells/zsh/lambda-mod-zsh-theme/default.nix
@@ -1,4 +1,4 @@
-{ stdenv, fetchFromGitHub }:
+{ stdenv, fetchFromGitHub, zsh }:
 
 stdenv.mkDerivation {
   name = "lambda-mod-zsh-theme-unstable-2017-10-08";
@@ -10,9 +10,13 @@ stdenv.mkDerivation {
     rev = "61c373c8aa5556d51522290b82ad44e7166bced1";
   };
 
+  buildInputs = [ zsh ];
+
   installPhase = ''
-    mkdir -p $out/share/themes
-    cp lambda-mod.zsh-theme $out/share/themes
+    chmod +x lambda-mod.zsh-theme # only executable scripts are found by `patchShebangs`
+    patchShebangs .
+
+    install -Dm0644 lambda-mod.zsh-theme $out/share/zsh/themes/lambda-mod.zsh-theme
   '';
 
   meta = with stdenv.lib; {
diff --git a/pkgs/shells/zsh/nix-zsh-completions/default.nix b/pkgs/shells/zsh/nix-zsh-completions/default.nix
index 3c4c3fabfd10..4405902ec3e0 100644
--- a/pkgs/shells/zsh/nix-zsh-completions/default.nix
+++ b/pkgs/shells/zsh/nix-zsh-completions/default.nix
@@ -15,15 +15,16 @@ stdenv.mkDerivation rec {
   };
 
   installPhase = ''
-    mkdir -p $out/share/zsh/site-functions
+    mkdir -p $out/share/zsh/{site-functions,plugins/nix}
     cp _* $out/share/zsh/site-functions
+    cp *.zsh $out/share/zsh/plugins/nix
   '';
 
-  meta = {
+  meta = with stdenv.lib; {
     homepage = https://github.com/spwhitt/nix-zsh-completions;
     description = "ZSH completions for Nix, NixOS, and NixOps";
-    license = stdenv.lib.licenses.bsd3;
-    platforms = stdenv.lib.platforms.all;
-    maintainers = [ stdenv.lib.maintainers.spwhitt stdenv.lib.maintainers.olejorgenb stdenv.lib.maintainers.hedning ];
+    license = licenses.bsd3;
+    platforms = platforms.all;
+    maintainers = with maintainers; [ spwhitt olejorgenb hedning ma27 ];
   };
 }