A 51-year-old man died after he was shot in the head at a motorcycle club in Mountfune, a rural area outside the village of Murroe.
It is believed a number of people were at the club when a man approached the victim and fired at least one shot.
The man was rushed to hospital, but was later pronounced dead.
It is understood the victim was from the area.
Police said it was too early to say what the motive was, and they are investigating a number of lines of inquiry, however, they do not believe it was gang-related.
The three men who were arrested were detained in the Limerick area late on Saturday night.
Two are in their late 40s and the other in his 20s.
Three men have been arrested in connection with a fatal shooting in County Limerick on Saturday.