Edwards grew up in Philadelphia, Pennsylvania and attended Imhotep Institute Charter High School. Edwards helped Imhotep win the Philadelphia City championship as a sophomore. As a junior, Edwards averaged 18.3 points and 8.3 rebounds per game and led the Panthers to the PIAA Class 5A state championship. That summer he played in the Nike Elite Youth Basketball League. He was also selected to play in the 2023 McDonald's All-American Boys Game and for Team USA in the Nike Hoops Summit.
As a senior, Edwards averaged 17.9 points and 7.5 rebounds and helped the Panthers repeat as state champions. He was named Mr. Pennsylvania Basketball and was a consensus 5-star prospect according to major recruiting services. After considering several offers including playing in the NBA G League, Edwards committed to Kentucky.
Justin Edwards did not have quite the season he was expected to have at Kentucky. He started 30 out of 32 games and only averaged 8.8 points and 3.4 rebounds. Even though his numbers were lower than expected, Edwards announced he was entering the NBA draft at the end of the season.