The US-initiated resolution was carried at the UN Human Rights Council in Geneva Thursday with 23 votes in favour and 12 against. Sri Lankan officials said the fact that another 12 nations abstained meant that a majority of the 47-member council did not support the censure move.
"Those 24 countries who refused to endorse the US resolution have sent a very clear and emphatic message rejecting imposition of external solutions on Sri Lanka," Ravinatha Aryasinha, Sri Lanka's top envoy in Geneva, told AFP by telephone.
Sri Lanka's state-run Daily News reported Thursday's UN vote under the headline: "Majority against America." The paper also called the UNHRC vote a "moral victory" for Colombo.
Sri Lanka President Mahinda Rajapakse, who rejected the UN call for an investigation against his country, told AFP Thursday that he was pleased that neighbouring India, which voted for a similar resolution last year, decided to abstain this time round. "I think it is encouraging that India did not vote against us," he said shortly after the results of the vote were announced.
"We reject this (resolution)," Rajapakse said. "This resolution only hurts our reconciliation efforts. It does not help. But I am not discouraged. We will continue with the reconciliation process I have started."
On Friday, Rajapakse ordered the immediate release of dozens of Indian fishermen detained for poaching in Sri Lanka's territorial water.
Sri Lankan diplomats described the move as a "thank you" to India for refusing to support the US-initiated resolution that set up the mechanism for a formal probe into Sri Lanka's war record.
Thursday's resolution is the third in as many years and is also the more damning for Colombo which has insisted that its troops did not kill a single civilian, but has also resisted calls for an independent external probe.
The latest resolution asked UN rights chief Navi Pillay to probe actions of both government forces and Tamil rebels during a seven year period leading up to the end of Sri Lanka's 37-year-old Tamil separatist war.
About 40,000 ethnic Tamil civilians were said to have been killed by government forces in the final months of fighting, a charge Colombo has vehemently rejected Sri Lanka has also said it needs more time to ensure reconciliation between the ethnic Tamil minority and the majority Sinhalese community.
On Wednesday, UN rights chief Pillay told the council that it was crucial to recall the "magnitude and gravity" of the violations allegedly committed by both the government and the rebels, notorious for their suicide bombings.
The 1972-2009 conflict claimed 100,000 lives, according to UN estimates.