Ellison visited the Panthers' campus three weeks ago and was scheduled to visit Virginia.
"Best fit overall as a school and definitely as a basketball program," he said of Pitt. "Coach [Kevin] Stallings is an amazing individual. Can relate to him."
Ellison, a 6-foot-6 shooting guard, averaged 7.4 points and 2.5 assists last season.
"They want me to come in and be a leader," he said. "I'll be one of the older guys. They see me as a guy who can help as an older guy. There will be a lot of young guys on the team."
Ellison will have two years of eligibility remaining after sitting out the 2017-18 season due to NCAA transfer rules.