The Total Recall actor cancelled a scheduled appearance on The Tonight Show in order to visit his family.
Speaking about his late uncle Tommy, he told host Jay Leno on Thursday: "My uncle passed away last week... and I got permission from the school principal, aka your good self, and made it home for a couple days."
Farrell explained that he was able to say goodbye to his uncle a few weeks prior to his death.
"I got to see him a few weeks before he died, I went home to Dublin about three weeks ago and he was in the hospice, so he wasn't in great shape.
"I brought him in a bottle of his favourite booze and he had his teeth out, so he looked like a hockey player. But we poured him a nice glass of Baileys, and that was the last time I saw him".
Colin Farrell will lead the cast of the upcoming remake of Total Recall, which is released at US cinemas on August 3 and August 29 in the UK.
He recently stated that the film poses a lot of "existential questions".
Watch a trailer for Total Recall below: