Dilshan was born in Kalutara to a family of a Malay father and a Sinhalese mother. He had his education at Kalutara Vidyalaya, Kalutara, where he started his cricket career as a teenager. Dilshan converted from Islam to Buddhism at the early age of 16, and was known as Tuwan Mohammad Dilshan before his conversion. However, his childhood coach Ranjan Paranavitana said even though Dilshan carried a Muslim name, he and his brothers and sisters followed their mother's religion from their childhood and once his parents separated he officially changed his religion and name.
Dilshan played his test debut against Zimbabwe on 18 November 1999 at Bulawayo. He scored only 9 runs, immediately lbw to Henry Olonga. However, he scored his maiden test century on the same series, in the second test. He scored an unbeaten 163* runs in the first innings, guided the team for the victory. Until retirement on 2013, Dilshan has played 87 test matches with 5,492 runs along 16 centuries and 39 wickets. His highest test score was at England, where he scored 193 runs at famous Lord's cricket ground, against England.
During the same tour to Zimbabwe in 1999, Dilshan also played his debut One-Day International against Zimbabwe on 11 December. He scored only 31 runs in his debut match. His first ODI century was against Netherlands on 4 July 2006. He smashed unbeaten 117* runs along with Sanath Jayasuriya, where Sri Lanka posted the highest ever ODI team score with 443 runs.
Dilshan played his almost all international matches as a middle-order all-round batsman in early years. But in 2006, he was willing to open the batting with Sanath Jayasuriya in ODIs, where he started to become a threatened batsman in all forms of the game. Since 2006, his stroke play with all sorts of aggression, he dominated the ODI arena in many magnificent occasions. Currently he is permanently act as an open batsman with bowling in crucial innings with incredible fielding abilities.
His trademark shot the he invented, Dilscoop was practiced a lot during the Indian Premier League 2009 tournament. His master stroke play was well acknowledged by many commentators, where he became one of the most aggressive batsmen of all time. He is also able to hit any ball coming in outside off, where his trademark cover drive is a lethal weapon against pace bowlers.
Dilshan was the top run scorer in the 2011 Cricket World Cup. He scored 500 runs from nine One Day international innings with a best score of 144 runs against Zimbabwe. He scored two centuries, two half centuries, 61 boundaries and four sixes during the tournament which ended at the Wankhede Stadium in Mumbai, India in April 2011. He was also the leading run scorer in many bilateral and triangular series held after the World Cups.
However, shortly after his appointment as captain, cricket fans and pundits in Sri Lanka questioned if he was the right man to lead Sri Lanka. However, Dilshan scored 193 runs against England at Lord's, where he broke the earliest record by highest score scored at Lord's by Sri Lankan.
Dilshan became the 5th player in international cricket that scored centuries in all forms of the game. During Australian tour of Sri Lanka in 2011, in twenty20 match he scored an unbeaten century of 104* from just 54 balls, becoming the 5th player to achieve that milestone after West Indian Chris Gayle, New Zealander Brendon McCullum, Indian Suresh Raina and fellow Sri Lankan Mahela Jayawardena and it is also the highest individual twenty20 international score by a Sri Lankan in the history. He scored the century from just 57 balls with 12 fours and 5 sixes. He achieved his century with a dilscoop hitting behind the wicket-keeper.
In December 2011, Sri Lanka registered their first ever Test wins in South Africa. This also became their first Test win under Dilshan's captaincy. However, after losing the Test series 2–1 and the subsequent ODI series 3–2, Dilshan resigned and was replaced by Mahela Jayawardene. In 2012, he was the second-heaviest scorer, with 1119 runs.
On 16 December 2014, on his 300 One-Day International, he scored his 18th One-Day International century and also passed the 9000 runs in ODIs. He became the 5th Sri Lankan and 15th overall to achieve the mark. He took 3 crucial wickets in the match and finally Sri Lanka ended up being the winners of the tournament. He won both man of the match award and man of the series award.
On 23 January 2015, Dilshan scored his 20th One-Day International century against New Zealand, becoming the 10th batsmen to score 20 ODI centuries.
On 26 February 2015, he scored unbeaten 161* runs during the group stage match of 2015 ICC Cricket World Cup against Bangladesh. This was his highest individual score in ODIs and this score was the highest score by a Sri Lankan in Cricket World Cup history, which was previously held 145 by Aravinda de Silva against Zimbabwe in 2003. This is also the highest individual score without a six in the ODI history. By this hundred, Dilshan became second only to Sanath Jayasuriya, by achieving 3 centuries over 150, as Sri Lankans, where Sanath has 4 150+ centuries in One-Day Internationals. During this innings, he also shared a 206* run second wicket partnership with Kumar Sangakkara. This was the highest second wicket partnership for Sri Lanka in ODIs.
On 1 March 2015, during the world cup group match against England, Dilshan took his 100th ODI wicket by caught and bowled Gary Balance, becoming the 3rd Sri Lankan to score 3000 runs and took 100 wickets after Jayasuriya and Aravinda.
Dilshan announced his retirement from Test cricket on 9 October 2013. However he mentioned that he will continue to play in the shorter format of the game until few international tours after 2015 ICC Cricket World Cup.
Dilshan publicly displayed his support to Mahinda Rajapaksa at the 2015 Presidential Election which has received severe criticism from some of his fans. He did so by welcoming Mahinda Rajapakse to Maharagama for an election rally.
Dilshan has 16 Test centuries, 21 One-Day International centuries, and 1 Twenty20 International century. He is the second Sri Lankan and fifth overall to achieve international centuries in all forms of the game.