The deal was completed earlier in the week, and Brown was officially introduced as the24th head coach in franchise history on Wednesday. Brown is the eighth coach to lead the Sixers since Larry Brown left in 2003.
Brett Brown was part of three NBA title teams with San Antonio. The 52-year-old Brown was an assistant under Gregg Popovich since 2002. He also coached the Australian men's national team from 2009-12, and played a key role in helping Manu Ginobili and Tony Parker develop into All-Stars with the Spurs.
Collins stepped down after the Sixers went 34-48, a year after advancing to the Eastern Conference semifinals.