On 11 August 2015, Antonio scored a brace in a 3–4 loss to League One club Walsall in the first round of the League Cup. On 15 August, the winger scored the winner in a 2–1 victory at home to Rotherham to open his tally for the new season. Having already rejected a bid of £4 million from West Bromwich Albion for the transfer of Antonio earlier that summer, Forest received a second bid of £4 million from arch-rivals Derby County. Consequently, Antonio was left out of Forest's Championship match against Charlton Athletic on 19 August 2015, with his manager Dougie Freedman citing that the winger was not "in the right frame of mind" to play. However, Antonio returned for the next league match at Bolton Wanderers. On 26 August, West Ham United joined the bidding for Antonio, offering Forest £4 million and winger Matt Jarvis on a season-long loan. On 1 September 2015, Antonio signed for Premier League club West Ham United for around £7 million on a four-year contract with an option for a further two years. He made his debut on 19 September, replacing Victor Moses in the 60th minute of West Ham's 2–1 Premier League win at Manchester City. In a Man of the match performance on 28 December 2015 in a 2–1 win, Antonio scored his first goal for West Ham. With the team losing 1–0 to Southampton, Antonio equalised when a clearance hit him and looped over Southampton goalkeeper, Maarten Stekelenburg. On 27 February, Antonio scored the only goal in a home win over Sunderland. He celebrated by lying on his side and spinning in a circle, imitating a celebration by "The Simpsons" character Homer Simpson in the episode "Last Exit to Springfield". In his next appearance, Antonio turned-in a Man of the match performance, scoring the only goal in a home win against Tottenham Hotspur. He followed this with another goal in a 3–2 away win at Everton three days later as West Ham came from two goals down. In July 2016, Antonio signed a new, four-year contract with West Ham. Antonio started West Ham's first match of the 2016–17 season in the right-back position, subsequently giving away a penalty in the early stages of the second half, which was converted by Eden Hazard, to give Chelsea a 1–0 lead. He was substituted not long after for Sam Byram. Chelsea went on to win 2–1. In the second match of the season, on 21 August 2016, Antonio returned to his favourite position of Winger.