In November 2017, he was named the One Day International (ODI) batsman of the year for the 2016–17 season at Sri Lanka Cricket's annual awards.

[11] In 2020, Mendis scored his maiden first-class double-century against Nondescripts Cricket Club and helped to draw the match.

[14] In October 2020, Mendis was drafted by the Kandy Tuskers for the inaugural edition of the Lanka Premier League.

[15] In November 2021, he was selected to play for the Galle Gladiators following the players' draft for the 2021 Lanka Premier League.

[clarification needed][22] Sri Lanka won the match by 106 runs, which was only their second Test win against Australia.

In the fifth match of the Tri-series in Zimbabwe against the West Indies, Mendis scored match-winning 94 runs and made 94-run partnership with Niroshan Dickwella.

[23] In the final against Zimbabwe, Mendis scored another fifty, guiding the team to win the series by 6 wickets.

[27] On 8 June 2017, against India in the 2017 ICC Champions Trophy, Mendis scored a match-winning 89 runs and made a 159-run stand for the second wicket with Danushka Gunathilaka.

[30] On 30 June 2017, against Zimbabwe, Mendis passed 1,000 ODI runs, becoming the joint second-fastest with Upul Tharanga for Sri Lanka to achieve this.

[35] After good performances in Tests against Bangladesh, Mendis was named to the T20I squad for Sri Lanka by replacing injured Kusal Perera.

His place in the team was in doubt with poor performances, and he was omitted from the England tour in Sri Lanka.

In the fourth ODI, he batted in the middle order and scored only 5 runs and England won the series 3–0.

Mendis along with Angelo Mathews batted all over the fourth day, which was the fifth time that the Sri Lankan pair had done that in Test history.

[49] During the two-match Test series against South Africa, Mendis continued his poor form with the bat with scores 0, 12 and 16.

He made 80 runs off 163 deliveries in the match and had a strong partnership with eventual double-centurion Angelo Mathews.

[58] In the second Test, Mendis scored his seventh century with an unbeaten 116 in the second innings, with Sri Lanka winning the series 1–0.

[62] All three players were seen in the city centre of Durham,[63] with SLC sending them all back home ahead of the ODI matches.

[65] Sri Lanka Cricket agreed to lift the ban early, rescinding the punishment in January 2022.

[67] On 23 May 2022, he was hospitalized after leaving the field holding his chest minutes before lunch on the first day of the second Test against Bangladesh.

[68][69] In the Australian Test series in July 2022, Sri Lanka suffered a huge defeat, with the match ending in three days.

[72] During the 2022 Asia Cup, Mendis played as the opener with Pathum Nissanka and they made match-winning partnerships in the games against Bangladesh, Afghanistan and India.

[76] In the first round in T20I World Cup 2022, against Netherlands, Mendis scored the 9th T20I half-century and made 79 runs in 44 balls hitting five boundaries and five sixes.

[78] On 5 January 2023, against India, Mendis scored his 11th T20I half-century and eventually Sri Lanka won the match by 16 runs.

[83] On 10th October 2023, against Pakistan, Mendis made his 3rd ODI century and scored 122 runs from 77 deliveries hitting 14 boundaries and 6 sixes.

[50] He was appointed as Sri Lanka's captain after regular skipper Dasun Shanaka was ruled out of the 2023 Cricket World Cup after suffering an injury in the game against Pakistan.

[87] In the next game against Afghanistan, Sri Lanka faltered big time, as their opponents eased past them with 7 wickets in hand.

He made an unbeaten century partnership with Kamindu Mendis, where Sri Lanka posted a mammoth total of 602 in the first innings.

[91] On 17 October 2024 against West Indies in the third T20I, Mendis made a match winning knock of an unbeaten 68 runs: his fifteenth fifty in T20Is, where he guided Sri Lanka to the victory and clinched the series 2–1.

[92] In July 2021, Mendis, along with Danushka Gunathilaka and Niroshan Dickwella, was found guilty of breaching the team's bio-secure bubble during Sri Lanka's tour of England.

[94] In December 2023, Mendis smashed a glass door at the Bloomfield Cricket Club pavilion after being dismissed for a 'duck' during an inter-club match.