Allen played college basketball for the Texas Longhorns, where he spent one season before declaring for the NBA draft. As a freshman, Allen was a standout player for the Longhorns, averaging 13.4 points and 8.4 rebounds per game. Despite his impressive numbers, the team struggled that season, finishing with a record of 11-22. Nonetheless, Allen's talent caught the attention of NBA scouts, and he was selected by the Brooklyn Nets with the 22nd overall pick in the 2017 NBA draft.

After spending three and a half seasons with the Nets, Allen was traded to the Cleveland Cavaliers in January 2021 as part of the James Harden trade. Since joining the Cavaliers, Allen has continued to impress on the court, averaging a double-double in points and rebounds per game. He was also named to his first NBA All-Star Game in February 2022, a testament to his hard work and dedication to the sport.

In conclusion, Jarrett Allen played college basketball for the Texas Longhorns before being selected in the first round of the 2017 NBA draft by the Brooklyn Nets. After three and a half seasons with the Nets, he was traded to the Cleveland Cavaliers in January 2021, where he continues to be a rising star in the league.