A.J. Johnson was born and raised in Fresno, California. He originally attended Woodland Hills(California) Taft. He had a strong 2021-2022 season averaging 16.7 points and 4.7 assists per game. He was enrolled to play at Donda Academy for this senior season, but the school founded by Kanye West was shuttered in late October 2022. He instead enrolled at Southern California Academy.
After finishing up his time at Southern California Academy, the 4-star prospect originally committed to play basketball at the University of Texas. However, he had a change of heart and elected to go Pro and play in the Next Stars program in Australia.
This season in 29 games playing for Illawarra, Johnson averaged 2.8 points, while playing 7.7 minutes per game.