Pruitt was pulled over around 3 a.m., hours after playing five minutes in the Celtics' 93-91 loss to the Los Angeles Clippers. He failed a field sobriety test, police said.
He was released at 8:30 a.m. on $5,000 bail, police Officer April Harding said.
Pruitt is from the Los Angeles area and played college basketball for Southern California.
"I sincerely apologize for my actions which have caused unnecessary embarrassment to my family, my team, and the Celtics organization," the 22-year-old Pruitt said in a statement issued by the team. "I used poor judgment and I am really disappointed in myself."
"I made a mistake and I have learned a valuable lesson," he said.
Pruitt was detained for stopping at a green light and because his Mercedes S550 had dark tinted windows that are illegal in California, Harding said.