on march 8, 2016, williams signed a 10-day contract with the phoenix suns. he made his nba debut on march 17 during a 103–69 loss to the utah jazz, recording one point and one steal in two minutes. the following day, he signed a multi-year deal with the suns. on april 9, he recorded a then season-high seven rebounds in a 121–100 win over the new orleans pelicans. in the suns' season finale on april 13, williams recorded his first double-double in the nba with season highs of 14 points and 12 rebounds (alongside 3 blocks) in a 114–105 win over the los angeles clippers.