It happened at a funeral for a woman in Rathass Cemetery in Tralee shortly before midday.
The first reports to the emergency services came in and said there was an altercation involving a group of people at the graveyard.
Gardaí responded and found a man in his 40s with critical injuries who was pronounced dead at the scene shortly afterward.
His remains were later removed to University Hospital Kerry where a post mortem will be scheduled.
They also discovered a seriously injured woman - the deceased man's wife - however her wounds are not understood to be life threatening.
She has also been taken to hospital for treatment.
The scene has been preserved by local Gardaí to facilitate a full forensic examination and an incident room has been set up at Tralee Garda Station.
Investigators are appealing to anyone who witnessed the altercation before midday at Rathass Cemetery to get in touch.