The Mad Men actor told MSNBC that the decision is part of his goal to make "green choices" in life.
"I've been a vegetarian for four years and I have chosen not to have children, which are both green choices in my life," he explained.
He also went on to reveal that he recently quit driving his car and now opts to walk or take public transport wherever possible.
"[Quitting driving] actually enriched my life," he said.
"It made my life better to slow down a little bit and walk through the city."