Jackson-Cartwright served as a backup to T. J. McConnell as a freshman, averaging 2.9 points and 1.8 assists per game. He split time with Kadeem Allen at point guard as a sophomore and averaged 5.2 points and 3.4 assists per game. Jackson-Cartwright averaged 5.9 points, 2.5 rebounds, and 4.1 assists per game as a junior, shooting 42.3 percent from behind the 3-point arc. In August 2017, he traveled with the team to Spain and was only feet away when the 2017 Barcelona attacks began, and ducked into a store until they ended. Coming into his senior season, he missed a practice and Pac-12 Media Day with a thigh contusion. On January 4, 2018, he scored a career-high 19 points in a 94-82 win over Utah. As a senior, Jackson-Cartwright averaged 7.8 points and 4.5 assists per game, shooting 41.7 percent from 3-point range. He finished his college career with 459 assists.