The Lakers announced the signings Thursday, the first day to formally sign new NBA contracts.
Williams and Bass are both 10-year NBA veterans who should bring stability to the Lakers, who are coming off the worst season in franchise history.
Williams was the NBA's Sixth Man of the Year last season with Toronto, averaging a career-best 15.5 points and 152 3-pointers. He also has played for Philadelphia and Atlanta.
Bass averaged 10.6 points and 4.9 rebounds last season with Boston. He spent the last four years with the Celtics after previously playing in New Orleans, Dallas and Orlando.
Brown was the 34th overall pick in last month's draft out of Stanford.