In February 2021, Iyer was bought by the
Kolkata Knight Riders in the
IPL auction ahead of the
2021 Indian Premier League. On 20 September 2021, upon resumption of the IPL in the
United Arab Emirates, he made his IPL debut against
Royal Challengers Bangalore. On 23 September 2021, he scored his maiden IPL fifty against
Mumbai Indians. Iyer emerged as a key player for KKR for the rest of the tournament, aiding in their run to the final, by scoring 370 runs at an average of 41 and a strike rate of 129. He was named as player of the match in the second qualifier, after scoring 55 runs and he followed this up with another half century in the final. Alongside his opening partner
Shubman Gill, he put on an opening stand of 91, which proved to be in vain as KKR lost the match. On 16 April 2023, Iyer scored his maiden IPL Century against Mumbai Indians scoring 104 runs in 51 balls. Thus, he become only the 2nd Batter to score a century for KKR after
Brendon McCullum did in the first match of
IPL 2008, 15 years ago, but his century went in vain as KKR was defeated by Mumbai Indians. On 24 November 2024, Iyer was bought back by Kolkata Knight Riders for Rs.23.75 crore, becoming one of the most expensive players in the history of the IPL. He was announced as the vice-captain of the team for the
2025 edition, succeeding
Nitish Rana. He was released by Kollata Knight Riders ahed of the 2026 IPL season, subsequently on 16 December 2025, Iyer was bought by
Royal Challengers Bangalore for Rs.7 crore. == International career ==