diff --git a/cmd/todoist/cmd/completion.go b/cmd/todoist/cmd/completion.go
index 521910b..ac6faa0 100644
--- a/cmd/todoist/cmd/completion.go
+++ b/cmd/todoist/cmd/completion.go
@@ -1,6 +1,7 @@
 package cmd
 
 import (
+	"fmt"
 	"github.com/spf13/cobra"
 	"os"
 )
@@ -12,14 +13,171 @@ var completionCmd = &cobra.Command{
 }
 
 var completionBashCmd = &cobra.Command{
-	Use: "bash",
+	Use:   "bash",
 	Short: "generate bash completion script",
 	Run: func(cmd *cobra.Command, args []string) {
 		RootCmd.GenBashCompletion(os.Stdout)
 	},
 }
 
+// Refs
+// - https://github.com/kubernetes/kubernetes/blob/master/pkg/kubectl/cmd/completion.go
+// - https://github.com/spf13/cobra/issues/107#issuecomment-270140429
+var completionZshCmd = &cobra.Command{
+	Use:   "zsh",
+	Short: "generate zsh completion script",
+	Run: func(cmd *cobra.Command, args []string) {
+		zshHead := "#compdef todoist"
+		zshInitialization := `
+__todoist_bash_source() {
+	alias shopt=':'
+	alias _expand=_bash_expand
+	alias _complete=_bash_comp
+	emulate -L sh
+	setopt kshglob noshglob braceexpand
+	source "$@"
+}
+
+__todoist_type() {
+	# -t is not supported by zsh
+	if [ "$1" == "-t" ]; then
+		shift
+		# fake Bash 4 to disable "complete -o nospace". Instead
+		# "compopt +-o nospace" is used in the code to toggle trailing
+		# spaces. We don't support that, but leave trailing spaces on
+		# all the time
+		if [ "$1" = "__todoist_compopt" ]; then
+			echo builtin
+			return 0
+		fi
+	fi
+	type "$@"
+}
+
+__todoist_compgen() {
+	local completions w
+	completions=( $(compgen "$@") ) || return $?
+	# filter by given word as prefix
+	while [[ "$1" = -* && "$1" != -- ]]; do
+		shift
+		shift
+	done
+	if [[ "$1" == -- ]]; then
+		shift
+	fi
+	for w in "${completions[@]}"; do
+		if [[ "${w}" = "$1"* ]]; then
+			echo "${w}"
+		fi
+	done
+}
+
+__todoist_compopt() {
+	true # don't do anything. Not supported by bashcompinit in zsh
+}
+
+__todoist_ltrim_colon_completions()
+{
+	if [[ "$1" == *:* && "$COMP_WORDBREAKS" == *:* ]]; then
+		# Remove colon-word prefix from COMPREPLY items
+		local colon_word=${1%${1##*:}}
+		local i=${#COMPREPLY[*]}
+		while [[ $((--i)) -ge 0 ]]; do
+			COMPREPLY[$i]=${COMPREPLY[$i]#"$colon_word"}
+		done
+	fi
+}
+
+__todoist_get_comp_words_by_ref() {
+	cur="${COMP_WORDS[COMP_CWORD]}"
+	prev="${COMP_WORDS[${COMP_CWORD}-1]}"
+	words=("${COMP_WORDS[@]}")
+	cword=("${COMP_CWORD[@]}")
+}
+
+__todoist_filedir() {
+	local RET OLD_IFS w qw
+	__todoist_debug "_filedir $@ cur=$cur"
+	if [[ "$1" = \~* ]]; then
+		# somehow does not work. Maybe, zsh does not call this at all
+		eval echo "$1"
+		return 0
+	fi
+	OLD_IFS="$IFS"
+	IFS=$'\n'
+	if [ "$1" = "-d" ]; then
+		shift
+		RET=( $(compgen -d) )
+	else
+		RET=( $(compgen -f) )
+	fi
+	IFS="$OLD_IFS"
+	IFS="," __todoist_debug "RET=${RET[@]} len=${#RET[@]}"
+	for w in ${RET[@]}; do
+		if [[ ! "${w}" = "${cur}"* ]]; then
+			continue
+		fi
+		if eval "[[ \"\${w}\" = *.$1 || -d \"\${w}\" ]]"; then
+			qw="$(__todoist_quote "${w}")"
+			if [ -d "${w}" ]; then
+				COMPREPLY+=("${qw}/")
+			else
+				COMPREPLY+=("${qw}")
+			fi
+		fi
+	done
+}
+
+__todoist_quote() {
+    if [[ $1 == \'* || $1 == \"* ]]; then
+        # Leave out first character
+        printf %q "${1:1}"
+    else
+		printf %q "$1"
+    fi
+}
+
+autoload -U +X bashcompinit && bashcompinit
+
+# use word boundary patterns for BSD or GNU sed
+LWORD='[[:<:]]'
+RWORD='[[:>:]]'
+if sed --help 2>&1 | grep -q GNU; then
+	LWORD='\<'
+	RWORD='\>'
+fi
+
+__todoist_convert_bash_to_zsh() {
+	sed \
+	-e 's/declare -F/whence -w/' \
+	-e 's/_get_comp_words_by_ref "\$@"/_get_comp_words_by_ref "\$*"/' \
+	-e 's/local \([a-zA-Z0-9_]*\)=/local \1; \1=/' \
+	-e 's/flags+=("\(--.*\)=")/flags+=("\1"); two_word_flags+=("\1")/' \
+	-e 's/must_have_one_flag+=("\(--.*\)=")/must_have_one_flag+=("\1")/' \
+	-e "s/${LWORD}_filedir${RWORD}/__todoist_filedir/g" \
+	-e "s/${LWORD}_get_comp_words_by_ref${RWORD}/__todoist_get_comp_words_by_ref/g" \
+	-e "s/${LWORD}__ltrim_colon_completions${RWORD}/__todoist_ltrim_colon_completions/g" \
+	-e "s/${LWORD}compgen${RWORD}/__todoist_compgen/g" \
+	-e "s/${LWORD}compopt${RWORD}/__todoist_compopt/g" \
+	-e "s/${LWORD}declare${RWORD}/builtin declare/g" \
+	-e "s/\\\$(type${RWORD}/\$(__todoist_type/g" \
+	<<'BASH_COMPLETION_EOF'
+`
+		zshTail := `
+BASH_COMPLETION_EOF
+}
+__todoist_bash_source <(__todoist_convert_bash_to_zsh)
+_complete todoist 2>/dev/null
+`
+		fmt.Println(zshHead)
+		fmt.Print(zshInitialization)
+		RootCmd.GenBashCompletion(os.Stdout)
+		fmt.Print(zshTail)
+	},
+}
+
 func init() {
 	RootCmd.AddCommand(completionCmd)
 	completionCmd.AddCommand(completionBashCmd)
+	completionCmd.AddCommand(completionZshCmd)
 }