Chandimal started his cricketing career as a teenager at Dharmasoka College, Ambalangoda. Later he moved to Ananda College, Colombo captaining its under-17 team. In 2008, he was appointed captain of the school's first eleven, which he led in 13 outright wins in a season, rewriting the history of Sri Lankan school cricket. He was the first schoolboy cricketer to exceed 1,000 runs, with an aggregate 1,580 runs, and won the Observer-Mobitel Schoolboy Cricketer of the Year Award in 2009. On leaving school, he joined the Nondescripts Cricket Club.
He scored 64, four and 109 in his first three innings for the Sri Lanka Cricket Development XI. He is an aggressive batsman who scored two centuries for his country's U-19s, which he vice-captained, and plays for the Sri Lanka Cricket XI and Schools Invitation XI for one day and Twenty20 cricket.
After also playing against New Zealand in a Twenty20 match in Florida, Chandimal was selected for an ODI tri-series in Zimbabwe, where the two sides also played India. He made his debut against Zimbabwe, scoring an unbeaten 10 as his side cruised to a nine-wicket win and then registered his maiden international century by scoring 111 runs off 118 balls against India, an innings that helped his side both win the match (by six wickets) and knock India out of the tournament. He also became the youngest Sri Lankan to score an ODI century.
Chandimal made his Test debut for Sri Lanka in December 2011, in the second Test of the series against South Africa in Durban. On debut he made half-centuries (58 and 54) in each of Sri Lanka's innings. This incidentally led Sri Lanka to their first Test win in South Africa.