His song Only Love Survives placed ahead of four other hopefuls on EuroSong 2013, on RTE's Late Late Show.
The Co Tyrone musician, who was the only entrant to perform his own composition, will now go forward to sing in Malmö, Sweeden, later this year.
He said: "I am thrilled to have been chosen to represent Ireland in the Eurovision Song Contest. A huge thank you to everyone who voted for the song tonight - I really appreciate it.
"I'd like to thank my family, friends and my mentor Stuart for all their support over the last few months. It's such an honour to have been chosen to represent Ireland at Eurovision.
"I can't wait to perform in Malmö in May."
The other acts who competed were Zoë Alexis Bohorquez, Inchequin, Kasey and Aimée Fitzpatrick, who was favoured by the judges before televoters picked Mr Dolan.
Last year X Factor twins Jedward finished eighth when they represented Ireland at the Eurovision in Baku, Azerbaijan, with an energetic performance of Waterline.
This year's UK entrant is yet to be announced.