On 22 January 2016, Amartey joined Premier League side Leicester City on a four-and-a-half-year contract for a fee around the region of up to £6 million. In his first season in his new country, Amartey featured five times as his team Leicester City won the Premier League title. He made his debut for the club on 27 February 2016, in 1–0 win over Norwich City at the King Power Stadium. In the 2016–17 season, Amartey became a first team regular following the departure of N’Golo Kanté. partnering teammate Danny Drinkwater in the central midfield role. While his workrate roughly equalled Kanté’s, he has been unable to match his tackles and interceptions. Amartey scored his first goal for Leicester in an 88th-minute equaliser away at Stoke City on 17 December 2016, salvaging a 2–2 draw. On 8 February 2017, just over 12 hours after returning to Leicester from international duty, Amartey played 120 minutes (including AET) in a 3–1 FA Cup fourth-round replay win over Derby County. In October 2018, Amartey broke his ankle in a game against West Ham, ruling him out for the rest of the 2018-19 season.