He has been a member of the West Indies cricket team since his Test debut against Pakistan at Barbados in May 2000 – a match in which he was unbeaten in both innings including a first innings score of 84 not out. He missed scoring his maiden Test century against South Africa in March 2001 when he was run out for 91. His score of 78 in the second Test against India at Chennai in October 2002 was his fourth innings of 75+ that was not converted into a century. His maiden Test century came in his next Test series against Bangladesh at Dhaka. His next Test century came against Australia at St. John's in May 2003. His best innings (291) came against England in February/March 2009. Sarwan is also a part-time leg-break bowler with best bowling figures of 4 for 37.
During the most recent controversy involving the bowling action of Sri Lanka great Muttiah Muralitharan, which led to an International Cricket Council investigation of most of the world's international-class bowlers, Sarwan was found to be the only bowler tested who did not transgress the Laws of Cricket regarding the straightening of the arm during delivery.
Sarwan was dropped from the side for the second Test against Pakistan in November 2006. It was the first time in his six-year career that he had missed a game due to poor form. According to captain Brian Lara "It wasn't designed as a drop. We just wanted to make him aware of the situation and come back stronger. We need him and we need him to take control."
On 29 April 2007 it was announced that Sarwan was to succeed the retiring Brian Lara as captain of the West Indies following the West Indies' exit from the 2007 Cricket World Cup.
During the second Test in the West Indies tour of England in May 2007, Sarwan injured his shoulder when he collided with the boundary fence while attempting to cut off a boundary. The injury was serious enough to rule him out of the remainder of the tour and for a further ten months. Sarwan returned to the West Indies side in 2008 for the home series against Sri Lanka, as vice-captain to the current captain, Chris Gayle. Throughout the series Sarwan showed excellent form with the bat, looking very fluent and scoring over 50 in four consecutive innings, including a match-winning century, at an average of 77.75.
In the 2008 Test series against Australia, Sarwan continued his fine batting form by following up with a half century and a matching saving 128 in the 2nd Test in North Sound, Antigua. At the age 28 years, 228 days he became the youngest West Indian to reach the 5000 runs milestone when he scored a century against England in Jamaica. In the 2009 home series against England, in scoring his 13th Test match century Sarwan equalled the record for the most centuries in the fourth innings – a record he shares with Sunil Gavaskar and Ricky Ponting, In the first innings of the fourth test he recorded his personal best of 291 which equalled the highest score for the West Indies of the great Sir Vivian Richards.
Sarwan's name is a common Hindu name shared by many of his countrymen who have roots in India. For much of his career he wore a bandanna under his helmet whilst batting, but has now dropped the practice due to a change in the design of helmet. He shares the habit of his fellow Countrymen Shivnarine Chanderpaul and Narsingh Deonarine of marking his guard with a bail.
Sarwan did however lose his central contract due to poor fitness and indifferent form. West Indies coach Ottis Gibson stated that leaving Sarwan out was a tough decision but he will make many contributions to the West Indies in the future and that he needs time to regain his form. Therefore he wasn't selected for the tour of Sri Lanka along with regular wicket-keeper Denesh Ramdin Having fallen out of international favour, he signed for English county Leicestershire for the 2012 English season.