On 14 February, Williams marked his 2015 Super Rugby return to the Chiefs with a victory over the Blues in the first round. Two weeks later, he scored his first try of the season against his former club, the Crusaders. On 13 June, after being sidelined for a month with a back injury, Williams returned in the final round of the regular season. The following week, Williams was part of the Chiefs' team that lost to the Highlanders in the quarter-finals. Despite having played only ten of the sixteen regular season games, Williams had the second most offloads, and his nine line-break assists were the highest of any player with ten matches or less.