His commitment comes one day after his father, Michael Porter Sr., accepted an offer to join Cuonzo Martin's staff at Missouri as an assistant coach.
"It's home," the younger Porter told ESPN on Friday. "I love the city, the fans and I feel like next year we can do something very special there."
Porter was released from his letter of intent by Washington on Thursday. He had committed to the Huskies in July, two months after his father became an assistant coach at Washington under Lorenzo Romar. Romar was fired last week after 15 seasons in Seattle.
The Porters lived in Missouri before heading to the Pacific Northwest, and the elder Porter was an assistant women's coach at Missouri for three seasons. The younger Porter's sisters play at Missouri, and his aunt is the head women's coach.
"It wasn't an easy decision at all, but I'm very comfortable with the program and Coach Martin," Porter told ESPN's Jeff Goodman. "I trust my dad. I think we have a chance to do something special. ... I'm excited beyond words."
His younger brother, Jontay, recently decommitted from Washington. He is ranked No. 26 in the ESPN 60 for 2018 but could reclassify to the 2017 class.
Porter said his brother hasn't decided whether he will reclassify and play with him this season at Missouri or play his senior year in high school.
ESPN's Jeff Goodman contributed to this report.