Gilkison, a rising senior at Kent State, and O'Reilly, a rising senior at Illinois, finished the 54-hole tournament at 11-under 205, three shots ahead of the rest of the field.
The pair matched scores until the par-5 15th, when Gilkison drew even with a birdie, only to give it right back with a bogey on the par-3 16th. The par-4 17th looked like it would be the key hole of the tournament, with a two-shot swing giving Gilkison a one-shot lead heading to the 54th hole. But again he gave it back with a bogey and the two went to extra holes.
In the three-hole aggregate playoff, Gilkison went 1 under to edge out O'Reilly and take the Northern Amateur title. With the win, Gilkison becomes the third Kent State player in the last six years, joining Chase Johnson and Ian Holt.
Josh Gilkison (L) and Brendan O'Reilly (Northern Amateur photo)
The defending champion, Mitch Davis of the University of Indiana, finished in a tie for third at 8 under par with Nate Vontz of Creighton University and Timothy Lim of Drake Unviersity.
Gilkison showed good form coming into the event, coming off of a 9th place finish in the Ohio Amateur.