The defender put pen to paper on a fresh two-year contract to extend his stay at Huish Park until the summer of 2019.
Former Southampton Academy product Mugabi made his professional debut in the EFL Cup against Walsall last August before marking the likes of Romelu Lukaku and Yannick Bolasie in the second round only weeks later.
He featured 39 times for the Glovers in his first year in Somerset and was thankful for the help boss Darren Way and assistant Terry Skiverton have given him since his arrival.
“I’m very delighted to sign my new deal,” Mugabi told YTFC.net.
“I can’t wait to join up with the boys in pre-season and crack on next year.
“The gaffer was a massive influence and Terry was as well. I worked a lot with Terry last season and improved a lot so I’m looking forward to working with both of them again.”