McDowell won the 2010 US Open at Pebble Beach, California
Graeme McDowell will not return home to play in the Irish Open as defending a PGA Tour title at the same time is "the best option for me" right now.
The absence of the former US Open winner is a blow to the Galgorm Castle tournament on September 24-27, which was moved from May due to Covid-19.
"I never failed to attend this amazing event for 18 years," he said.
"Due to the necessary changes to the event, travel and schedule, I choose not to play this year."
This year's Irish Open was originally scheduled for Mount Juliet in Kilkenny, but it fell victim to the coronavirus pandemic.
The Irish Government's Covid-19 restrictions resulted in the location of Galgorm Castle Golf Course being confirmed as the new host.
Open champion Shane Lowry, who won the tournament as an amateur in 2009, was boosted on Tuesday by confirming his entry into Ballymena.
McDowell has made the "very difficult decision" not to join fellow countryman Lowry as he defends the Corales Punta Cana Resort and Club Championship title in the Dominican Republic.
"Defending a title is something special and an honor I've taken seriously throughout my career," added the Portrush man, who also apologized to tournament sponsors for his absence. .
"Under normal circumstances, defending this event would not be a priority over playing my home Open, but the unprecedented circumstances make this a better option at this time."
"We will hopefully be back in 2021, with the event in full blast, surrounded by big Irish fans, assuming we can get past the problems caused by Covid."