Shreyas Iyer was born on 6 December 1994 in Mumbai to Santosh Iyer, who has his roots in Kerala, and Rohini Iyer, a Mangalorean Tuluva. In an interview with The Hindu, Iyer mentioned that his ancestors are from Thrissur, Kerala. He was educated at Don Bosco High School, Matunga and at Ramniranjan Anandilal Podar College of Commerce and Economics, Mumbai.

In 2014, Iyer represented Trent Bridge Cricket Team. During a trip of the UK, he played three matches scoring 297 runs at an average of 99 with a highest score of 171, a new team record.

Iyer made his List A debut for Mumbai in November 2014, playing in the 2014–15 Vijay Hazare Trophy. He scored 273 runs in that tournament at an average of 54.60. Iyer made his first-class cricket debut in December 2014 during the 2014–15 Ranji Trophy. He scored a total of 809 runs in his debut Ranji season at an average of 50.56 including two centuries and six fifties. He was 7th highest scorer of 2014–15 Ranji Trophy.

In February 2015, Iyer was signed in the 2015 IPL players auction by the Delhi Daredevils for 2.6 crores (approximately $430,000). Thus Iyer became the highest earning uncapped player in the tournament. He scored 439 runs in 14 matches, with a 33.76 average and a strike rate of 128.36, making Iyer the 9th most consistent player and Emerging Player of 2015 IPL.

In March 2017, Iyer was added to India’s Test squad as cover for Virat Kohli, ahead of the fourth Test against Australia. He came on as a substitute fielder in the fourth test and ran out Stephen O’Keefe for 8.

In October 2017, Iyer was named in India’s Twenty20 International (T20I) squad for their series against New Zealand. He made his T20I debut for India against New Zealand on 1 November 2017, but he did not bat. On 4 November 2017, he got his first batting opportunity and scored 23 runs in 21 balls.

In November 2017, Iyer was named in India’s One Day International (ODI) squad for their series against Sri Lanka. He made his ODI debut for India against Sri Lanka on 10 December 2017. Shreyas also played in January 2018 for India against South Africa in the one day internationals. In August 2019, he scored 71 and 63 against West Indies in 2nd and 3rd ODI whereas 1st ODI was abandoned because of rain. He was the second-highest run-getter in the series after Virat Kohli.

In September 2018, Iyer was named as the vice-captain of Mumbai for the 2018–19 Vijay Hazare Trophy tournament. He was the leading run-scorer for Mumbai in the tournament, with 373 runs in seven matches. In October 2018, Iyer was named as the captain of India B’s squad for the 2018–19 Deodhar Trophy. He was also the leading run-scorer in the Deodhar Trophy, with 199 runs in three matches.

Iyer was retained by Delhi Daredevils in the 2018 IPL Auction. On 25 April 2018, he was announced as the new captain of Delhi Daredevils replacing Gautam Gambhir. On 27 April 2018, he became the youngest captain to lead the Delhi Daredevils team in the IPL history at the age of 23 years and 142 days during the match against Kolkata Knight Riders and was also the fourth overall youngest to captain any IPL side. On his IPL captaincy debut, Shreyas Iyer smashed an unbeaten match winning knock of 93 off 40 deliveries with 10 sixes, which was his third successive IPL fifty of the season to power DD to a heavy total of 219/5 in the first innings of the match before earning him the man of the match award. Under his captaincy, Delhi Daredevils managed to defeat KKR by 55 runs to secure only their second win of the tournament. Iyer was retained by the Delhi Capitals in the IPL 2019 Season which he led the team into the playoffs for the first time after seven years.

In February 2019, in the opening round of the 2018–19 Syed Mushtaq Ali Trophy tournament, Iyer made the highest total by an Indian batsman in a T20 match, when he scored 147 runs.

On 18 December 2019, in the second ODI against the West Indies, Iyer scored 31 runs in one over, the most scored by a batsman for India in a single over in ODIs.

In the 2020 season, he continued as the captain for Delhi Capitals.

On 24 January 2020, in the first T20I against the New Zealand, Iyer scored an unbeaten 58 off 29 balls and was declared the Man of the Match.

On 26 January 2020, in the second T20I against the New Zealand, he scored 44 off 33 balls. On 5 February 2020, in the first ODI against the New Zealand, Iyer scored 103 off 107 balls, his maiden century in ODI cricket.