The Castledawson man has won one up against the 2013 Irish Boys champion Robin Dawson from Waterford in the final of the Cathedral Eye Clinic sponsored championship.
Selfridge had looked to be cruising to his second successive win at the North, two up after nine but Dawson pegged him back with wins at the 10th and 12th.
Selfridge took an ultimately telling lead on the 17th with a par five after Dawson had to take a penalty drop when his ball went into the bushes at the back of the green.
The 22-year-old closed out the win with a five on the last.
Earlier in the tournament, he saw off Matthew McClean (Balmoral) and Darragh Coghlan (Portmarnock) before beating Castlerock golfer David Mulholland three and two in the semi-final on Friday morning.
The +3 handicapper is the first man to win the prestigious tournament two years on the trot since Warrenpoint's Paddy Gribben triumphed in 1998 and 1999.
Last year, Selfridge beat another Waterford man in the final, coming out with a two and one win over Gary Hurley.