He played college basketball for the Cal State Northridge Matadors, the Oklahoma Sooners and the UNLV Runnin' Rebels.

Harkless attended Etiwanda High School at Rancho Cucamonga, California, leading his team to a 30–4 and a third-place finish at the CIF Southern Section Open Division Tournament as a senior while averaging over 10 points and five assist.

[6] He played 20 games and averaged 11.6 points, 3.9 rebounds, 3.2 assists and 1.0 steals in 22.6 minutes while shooting 47.5% from the field.

[5] On April 25, 2024, Harkless signed with the Saskatchewan Rattlers of the Canadian Elite Basketball League[5] where he played 27 games and averaged 11.4 points, 3.7 rebounds, 2.9 assists and 1.0 steals in 20.7 minutes.

After joining them for the 2024 NBA Summer League,[8] on September 4, 2024, Harkless signed with the Los Angeles Clippers.