Coach Kevin Willard announced the move on Monday, noting he can play next season.
Harris had an outstanding season in 2020-21, averaging 20.5 points and 3.5 assists. He led the nation in average minutes played (38.9) and 3-pointers (3.9). He shot 47 percent from the field and 44 percent from 3-point range, seventh best in the country.
The former scholastic player at The Patrick School will have two years of eligibility left.
Seton Hall posted a 14-13 record this past season, finishing fourth in the Big East in the regular season. The Pirates did not make the NCAA for the first time since 2015. They also elected not to play in the NIT.