Champions Dromore had no answer to the passion of the men from Dunmoyle as they swept forward in the closing 20 minutes.
Dromore dominated during the opening 10 minutes, but managed just one point, a superb Ryan McMenamin effort from wide on the right.
Errigal drew level through Ronan McCrory in the ninth minute, and Davy Harte was once again the provider as Bryan Horisk cancelled out Sean McDonnell’s score.
Enda McGinley and Tommy Canavan battled for possession around midfield as Errigal grew in confidence and committed men to the attack, going in front for the first time through Caolan Tierney.
Full-back Michael McCrory pushed up to slot over a point, and the champions were 18 minutes without a score when Niall Sludden finally found a way through to slot over a point.
Errigal led 0-5 to 0-3 at the interval, but the O’Neill Cup holders exploded into action on the restart, hitting the first four points of the second-half to go back in front, the pick of them a Colm McCullagh effort, floated delightfully between the posts.
But Errigal stepped up the tempo, with Davy and Peter Harte inspiring with their strong running from the back.
Both thumped over inspirational scores as the challengers proceeded to outscore the champions by eight points to one in the final quarter.
Ronan McCrory, a tireless worker all afternoon, punched over his second poinmt, and Damian ‘Daisy’ McDermott got his name on the scoresheet.
Cormac McGiney punched the air after slotting over the 59th minute point which he knew made Dromore’s task impossible.
Dromore finished with 14 men when Cathal McCarron received a straight red card, as Errigal deservedly strode to victory.
Scorers for Errigal Ciaran: T Canavan 0-3 (2f), B Horisk, R McCrory 0-2 each, M McCrory, D Harte, D McDermott, C Tierney, C McGinley , P Harte 0-1 each.
Scorers for Dromore: E McCusker 0-3 (3f), N Sludden, C McCarron, C McCullagh, R McMenamin, S McDonnell 0-1 each.
ERRIGAL CIARAN: J Devine, A McCrory, M McCrory, C Quinn, S Tierney, P Harte, D Harte, Cormac McGinley, E McGinley, Ciaran McGinley, T Canavan, C Tierney, D McDermott, B Horisk, R McCrory.
Subs: D Canavan for C Tierney, P Quinn for S Tierney.
DROMORE: P Ward, F O’Neill, S O’Neill, K Donnelly, C O’Hara, R McMenamin, C McCarron, H McNulty, S McDonnell, N Sludden, R McNabb, E O’Neill, P Montague, E McCusker, C McCullagh.
Subs: C O’Neill for Montague, T McCarron for E O’Neill.
Referee: C O’Hagan (Brackaville).