Baker's AAU coach, Ryan Silver, confirmed the news to ESPN.
Baker, a 6-foot-5 shooting guard from Roosevelt High School in Eastvale, California, is ranked No. 65 in the ESPN 100 for 2017. He signed with California in the fall, but reopened his recruitment when head coach Cuonzo Martin left for Missouri.
Kentucky immediately became involved, offering a scholarship to Baker over the weekend. Oregon, Marquette, Arizona, Maryland and Utah all met with Baker following his decommitment.
Baker joins a Kentucky class that includes five-star recruits Nick Richards (No. 11), P.J. Washington (No. 14), Quade Green (No. 22) and Jarred Vanderbilt (No. 23), in addition to four-star guard Shai Gilgeous-Alexander (No. 32). Five-star wing Hamidou Diallo will also be eligible next season after enrolling in January and sitting out the spring semester.
With De'Aaron Fox, Malik Monk and Isaiah Briscoe all declaring for the NBA draft, Kentucky coach John Calipari entered the spring wanting another perimeter shooter for next season. Baker fills that role, as he averaged 16.8 points and shot 47.7 percent from 3-point range with Earl Watson Elite on the Under Armour Association circuit last spring and summer.