Yoon is openly gay and has been a vocal advocate for greater inclusion of and support for diverse members of the STEM community throughout his career. Yoon is a long time member of the UW-Madison Committee on LGBT Issues, which he chaired between 2013 and 2014. He has also given numerous invited lectures on topics relating to being LGBTQIA+ in STEM. Yoon lives in Madison, Wisconsin with his husband, Michael Velliquette, who is an artist.