Johnson wrapped up his senior campaign at Ypsilanti High School with averages of 13.6 points, 9.6 rebounds, 5.3 blocks and 4.1 assists per game.

During his three-year tenure with the Cards, Johnson made a total of 88 appearances, starting in 22 games his sophomore season[6] and in 26 as a junior.

In late April 2017, he announced his decision to skip his senior year to start his professional career and declare for the 2017 NBA draft.

After going undrafted in the 2017 NBA draft, Johnson signed a training camp deal with the Chicago Bulls.

[14] On November 4, 2017, Johnson was included in opening night roster of the Windy City Bulls.

[20] On September 4, 2019, Johnson signed with Hapoel Holon of the Israeli Premier League for the 2019–20 season.

Jaylen Johnson scored 30 pts in loss against Boogie Cousins and The Taiwan Bears in June 2024.

During summer 2024, he signed with Hapoel Haifa of the Israeli Basketball Premier League (ISBL).