Lamb, a 6-foot-5 junior, started 32 games for the Bruins last season but underwent surgery to repair cartilage in his knee just before this season. He played in the season opener but experienced swelling and hasn't played since.
"We are very sad to see Tyler leave our program," coach Ben Howland said in a statement. "He is a great kid, and we have really enjoyed having him play for UCLA. We fully support his decision, and we wish him all the best in the future."
Lamb entered this season having averaged 5.8 points, 2.3 rebounds and 1.9 assists per game through 67 games in his career. He averaged nine points, 36 rebounds and 2.8 assists last season, when he played 31.4 minutes a game. He was second on the team with 43 3-point baskets made last season.
"I believe that it is in my best interest to find a new destination where I can continue to grow, both as a person and as a basketball player," Lamb said in a statement. "I am eternally grateful to my coaches and teammates for everything they have given me, and I wish them the best going forward. I plan on enrolling in a new educational institution by next semester, and I have not yet determined my schools of interest."