Brown became the franchise's 24th head coach, replacing Doug Collins, who resigned in April after three seasons at the helm.
Sixers General Manager Sam Hinkie said Brown, who spent seven seasons under Spurs head Coach Gregg Popovich, is the right fit for the team.
"We went through an exhaustive search to find the right head coach for our organization; one who had a passion for developing talent, a strong work ethic to help create the kind of culture we hope for, and a desire to continually improve. Brett has all of that," he said.
Philadelphia went 34-48 last season under Collins, who is expected to stay on in an advisory capacity.
Since his departure, the Sixers have committed to overhauling the roster, include a trade of all-star point guard Jrue Holiday to New Orleans for the sixth overall pick in the 2013 draft, which turned out to be 7-foot center Nerlens Noel, as well as a 2014 first-round draft choice.
"We all know the pain of rebuilding is real," Brown said. "It isn't something that happens quickly. There needs to be a patience and there needs to be a tolerance. We need a staff and a mentality that is heavily, heavily focused on development."