Mahinda Rajapaksa's regime is accused of committing atrocities against its own people in the final weeks of his country's 26-year civil war. There had been concern his presence could overshadow Monday's event.
But while Mr Rajapaksa, who holds the position of Chair in Office of the Commonwealth until next year, will stay away, the Department for Culture, Media and Sport (DCMS), which is helping to organise the event, said Sri Lanka would be represented by the country's UK High Commissioner.
David Cameron has described the allegations against the Sri Lankan government as "appalling" and "chilling" and warned the regime to investigate the accusations or face an international inquiry. The rejection of that ultimatum triggered a United Nations inquiry, which the Rajapaksa government is refusing to recognise.
Campaigners welcomed the news that the leader of a regime accused of war crimes would not attend an event to remember those killed in conflict.
Fred Carver, campaign director for the Sri Lanka Campaign For Peace And Justice, said: "The President of Sri Lanka, the chair of the Commonwealth, is clearly an international embarrassment, and that in turn is an embarrassment for the Commonwealth."
He added: "It is not enough for those responsible for war crimes to merely be shunned on the international stage. The British Government needs to work to bring them and their henchmen to justice."
Shadow Foreign Secretary Douglas Alexander said he also welcomed the confirmation, adding: "I have expressed deep reservations about President Rajapaksa's suitability to represent the Commonwealth, especially as Sri Lanka remains a designated 'country of concern' in the UK's annual Human Rights report."
A spokesman for the DCMS, which is co-ordinating the service alongside Glasgow City Council, said Mr Rajapaksa had been invited but would not attend. He added: "Sri Lanka will be represented by the High Commissioner in London".
The President has reportedly been reluctant to travel to Glasgow for the Commonwealth Games due to security fears.
Last week several hundred people gathered outside the opening ceremony at Celtic Park calling for the country to be suspended from the Games. Police warned there could be other protests if Mr Rajapaksa did attend the service.
Monday is recognised by the UK Government as a day of national commemoration for the First World War.
The service, to be led by Dr Laurence Whitley, will be followed by a procession to the Cenotaph in George Square for a wreath-laying service and march-past. The Cathedral service will also be shown live in George Square.
There will also be a commemoration at the Commonwealth War Graves Commission's St Symphorien cemetery in Mons, Belgium, where the first and last British soldiers who died on the Western Front are now buried.
Many political leaders are expected to remain in the city after watching their countries compete in the Commonwealth Games.
See Monday's Herald for a 28-page First World War supplement.