diff --git a/.zshrc b/.zshrc
index f6df398..8fd021d 100644
--- a/.zshrc
+++ b/.zshrc
@@ -17,7 +17,10 @@ if [[ -f "$oh_my_zsh/oh-my-zsh.sh" ]]; then
 	)
 
 	if [[ $(command -v tmux) ]]; then
-		if [[ ! -v "ZSH_TMUX_AUTOSTART" ]]; then export ZSH_TMUX_AUTOSTART=true; fi
+		# Only start/attach if no existing session with client.
+		if [[ (( $(tmux list-sessions -F "#{session_attached}" 2>/dev/null || echo 0) = 0 )) && ! -v "ZSH_TMUX_AUTOSTART" ]]; then
+		export ZSH_TMUX_AUTOSTART=true
+		fi
 		plugins+=(tmux)
 	fi