However, the 36-year-old insists he had already made a decision not to go to Rio de Janeiro as his wife is pregnant and due to give birth around the same time as the Games in Brazil.
“I woke yesterday morning to the news that Rory McIlory had withdrawn from the Irish Olympic Golf team, putting me in line for an automatic spot on the team,” said McDowell in a statement on Twitter.
“As many within golf will know my wife Kristin is pregnant and is due to have our second child just a couple of weeks after the Olympic Golf competition concludes.
“I made the decision many months ago, before I was on the team, that I would not play or travel outside the US, where I and my family live, in the weeks running up to the birth
“Unfortunately I will therefore not be available to replace Rory on the team. I have informed Paul McGinley and the Olympic Council of Ireland of my decision.”
In the absence of both McIlroy and McDowell three-time major winner Padraig Harrington is set to represent Ireland this summer alongside Shane Lowry.
“The Olympic Council of Ireland (OCI) respects the decision taken by Graeme McDowell to make himself unavailable for consideration for the Irish Olympic Golf Team,” said a statement from the OCI.
“It is important to re-emphasise that Graeme’s decision was taken for personal reasons as Rio 2016 is a matter of weeks before the birth of his, and his wife Kristin Stape’s, second child.
“This now presents a significant opportunity for another talented Irish golfer to represent his country and participate in golf’s historic return to the Olympic Games after a 112-year absence.
“In particular, we are very fortunate to have a global star in Padraig Harrington who is now in contention for automatic selection for Rio 2016.”
Harrington, the winner of two Open Championships and the US PGA, admits he will be honoured to represent his country.
“Based on the current ranking points I am next in line for automatic selection to the Irish Olympic Team for Rio 2016,” he said in a statement.
“I will work very hard over the next few weeks to achieve this selection as it would be a huge honour for me to represent Ireland at the Olympic Games, having played an active role in golf’s bid to be re-included in the Olympic Games programme.”
The International Golf Federation noted the “unique circumstances” leading to McDowell’s withdrawal.
“We recognise the unique circumstances for Graeme and his family and, while we are disappointed that he is not available for the Olympic Games, we sympathise with his position,” it said in a statement.
“There are many considerations for players but those who compete will have the opportunity to be part of a truly global celebration of sport.”