Williams, 42, pleaded guilty Friday to a misdemeanor count of driving while intoxicated in the Jan. 5 wreck and was immediately sentenced to the maximum possible term.
The former New Jersey Nets player will serve it after finishing a five-year prison term in New Jersey for accidentally shooting his limo driver.
"It seems excessive, but it's a small price to pay if it helps to deter drunken driving," Williams told Manhattan Criminal Court Judge Rita Mella in court. "I'll be the poster child for that if it's going to save lives."
Williams, who retired from basketball in 2000, had a blood-alcohol level more than twice the legal limit after his Mercedes-Benz SUV crashed into a tree around 3 a.m. on Jan. 5 near a Manhattan highway, prosecutors said.
Police found him sitting in the passenger seat. He told them someone else was driving and had left, but prosecutors have said surveillance video and witnesses establish he had been alone in the car.
The wreck happened the week before Williams pleaded guilty in New Jersey to aggravated assault for fatally shooting driver Costas Christofi.
Williams said his double-barreled 12-gauge shotgun went off while he was showing it to friends. He acknowledged he hadn't checked the safety mechanism.
Williams played nine seasons with the Philadelphia 76ers and the Nets before a leg injury forced his retirement. He was in the second year of a six-year, $86 million contract with the Nets.
He became an NBA analyst for NBC but was suspended after the shooting.
One of his lawyers, Oscar Holt III, told the Daily News earlier this week that Williams wants to put the DWI case behind him so he "can continue to work on changing the course of his life."