Lampard extending his stay in Manchester prompted an angry response from fans in New York, with New York City FC being accused of dishonesty for using the player in their promotional material and MLS Commissioner Don Garber being accused of poor leadership and a lack of transparency in his handling of the affair. On 1 January 2015, Manchester City head coach Manuel Pellegrini hinted that Lampard could extend his stay at Manchester City to a second season. On 9 January, Manchester City admitted that Lampard had never signed a two-year contract with New York City FC having instead originally signed a non-binding "commitment" to join the team. On the same day, Lampard confirmed his intention to begin playing for New York City FC at the end of the 2014–15 Premier League season. Around 300 people asked for season ticket refunds in response to the affair, while the 2015 MLS SuperDraft started a chant of "Where's Frank Lampard?" from the crowd.
On 1 January 2015, the day after extending his stay with the club, Lampard scored the winner for City in a Premier League encounter against Sunderland. On 14 March 2015, Lampard made his 600th Premier League appearance, becoming the second player to do so after Ryan Giggs, coming on as a substitute during City's 1–0 defeat to Burnley. On 24 May, Lampard captained Manchester City in their final match of the season and the last of his spell with the club. He scored his 177th Premier League goal to give City the lead in an eventual 2–0 win over Southampton at the City of Manchester Stadium and was substituted for Jesús Navas in the 77th minute.
On 10 January 2015, Lampard signed a pre-contract to play for New York City in MLS, beginning on 1 July. Injury delayed his debut until 1 August, when he came on as a 69th-minute substitute for Andrew Jacobson in a 3–2 defeat to the Montreal Impact at Yankee Stadium. In July, Lampard was one of the 22 players to be named to the 2015 MLS All-Star Game roster. On 16 September, he scored his first MLS goal as his team beat Toronto 2–0 to end a three-game losing streak. Eleven days later, Lampard scored the opening goal in a 2–1 victory over the Vancouver Whitecaps in the 29th minute of play; he was later also fouled in the area in the final minute of stoppage time, which allowed David Villa to convert the match-winning goal from the resulting penalty. On 2 October, he scored New York City's fastest ever goal in MLS history in a 2–1 away defeat to D.C. United. The team finished its debut season outside a place for the MLS Cup Playoffs, which drew criticism from some in the media, who expected more from the club's trio of designated players composed of former Champions League winners Lampard, David Villa and Andrea Pirlo.
From 2015 until 2017, Lampard served as a team captain on the ITV comedy panel show Play to the Whistle alongside Bradley Walsh. He was a regular pundit for football on BT Sport. For the 2018 World Cup, Lampard was among the BBC's list of pundits as he insisted that it would not affect his managerial duties.
He was awarded an OBE in the Queen's Birthday Honours on 13 June 2015. Lampard published his autobiography, Totally Frank, in 2006. He has written a series of children's novels about a footballer, Frankie, and his adventures with his magic football.
Lampard married Christine Bleakley, a Northern Irish broadcaster, on 20 December 2015. On 21 September 2018, they had a baby girl, Patricia Charlotte Lampard.