Pirates coach Kevin Willard made the announcement Thursday.
The 6-foot-8 Jackson will sit out the 2020-21 season and have three years of eligibility beginning in 2021-22.
Willard said Jackson can shoot the 3-pointer and also take the ball to the rim. Jackson, who's from Detroit, played in 26 games at Missouri, averaging 2.9 points, 1.8 rebounds and 8.1 minutes.
The Pirates recently added Harvard guard Bryce Aiken as a graduate transfer.
Seton Hall posted a 21-9 record last season and finished tied for first place in the Big East Conference.