Muralitharan, 32, has personally lead convoys of trucks carrying food in the country's remote corners where an estimated 30,000 lost their lives in the December 26 tsunamis and thousands are still missing.
"His life has been taken over by the disaster and he has an almost evangelical desire to help those that are suffering," recounted journalist Charlie Austin who accompanied the cricketer on a three-day relief mission last week.
"Murali has spearheaded the distribution of approximately 210 tonnes of flour, rice, sugar and lentils to the north-east and now the east," Austin wrote on the Cricinfo website.
"Murali signed up as a World Food Programme ambassador last year. The agency would have hoped for a couple of photo shoots and the odd public appearance.
"But they got a crusader, not an ambassador."
Muralitharan's company on the trip to Trincomalee in the north-east included fellow Sri Lanka cricketers Mahela Jayawardena and Kumar Sangakkara, and the Melbourne-based surgeon David Young, who operated on the off-spinner's damaged shoulder last year.
Having the country's most loved cricket star - and the lone Tamil in the team - direct relief operations helped, Austin recalled.
"When a police official tried to redirect some of the 90 tonnes of food into the government's own stores, Murali took the lead and dismissed the policeman brusquely, insisting the food was going to the people and nowhere near a government warehouse," the journalist wrote.
"Like many, he had heard rumours that some aid was being siphoned off into local markets and he was fearful about corruption."
At a refugee camp in Kinniya, a small village 20km south of Trincomalee badly hit by the floods, people ignored the visit of a cabinet minister and directed their attention towards the celebrated cricketer.
"The minister's appearance was poorly timed," Austin wrote. "While people thronged around Murali, bombarding him with questions and autograph requests, the politicians sloped off sulkily."
Muralitharan will take a break from his relief efforts to travel to Melbourne this week to play for Asia in a One-day charity match for tsunami victims against the World team on Monday.
He had last year declined to tour Australia for a Test series following adverse comments from Australian Prime Minister John Howard, who had labelled Muralitharan a "chucker".
"Next week, almost as soon as he's reeled off his 10 overs in Melbourne, Muralitharan will be back in front of a convoy, this time shepherding food down the south coast, especially around Galle," Austin wrote.
The cricketer was himself lucky to survive the disaster after keeping an appointment to attend an annual children's charity event in Galle on January 26.
Muralitharan, accompanied by his brother, mother and fiancee, were on way to Galle when they were asked to turn and head back to Colombo as the waves began to rise.
"Miraculously, he stayed just ahead of the devastation that was working its way up the coastline," Austin wrote.
But 50 children who were travelling by bus to attend the charity function were washed away into the sea and are presumed dead.