Following the NRL season, Williams announced himself unavailable for international selection. As a result, New Zealand named a 24-man squad without him; however, after reversing his self-exclusion he was added to the squad at the expense of Tohu Harris. On 27 October, Williams played in his first Test game in over five years—and his first victory for the Kiwis—while playing against Samoa. In his second game of the tournament, Williams scored three tries against Papua New Guinea, in a man-of-the-match performance. In the week leading up to the final, Williams was awarded the Rugby League International Federation's 'International Player of the Year' award for 2013; he cried when his teammates performed an impromptu haka for him at the award ceremony. He went on to play in the World Cup final, where New Zealand were defeated by Australia.