Cavan recovered from a double-whammy on the three-quarter hour mark to book their place in this year's Cadbury's Ulster U-21 FC final.
In front of around 2,000 fans at Brewster Park, Enniskillen, the winners-elect had centre-back James McEnroe sent-off before conceding a goal less than a minute later.
McEnroe walked for a second yellow card offence but it was David Millar's goal for Monaghan seconds later that seemed destined to propel the Oriel county into a final meeting with Donegal this coming Wednesday.
However 14-man Cavan bravely circled the wagons thereafter to score three unanswered points to finish in front after a thrilling encounter.
Fitful Cavan seemed determined to make life hard for themselves after blitzing their way into a compelling 1-5 to 0-0 lead after 13 minutes. Kieran Hughes pointed in the 16th minute to break Monaghan's duck and four more points served to cut Cavan's lead to 1-5 to 0-5 at the interval.
A Declan McKiernan free in the 34th minute ended a 21 minute barren spell for Cavan but Monaghan had the momentum and Donal Hahessy and Daniel McNally both pointed in the run-up to Millar's precise finish.
Amazingly, Millar's mercurial touch was to be Monaghan's final score as Cavan finished with a flourish with unanswered points from Fitzpatrick, Maloney-Derham and Givney to finally put their opponents to the sword.
Cavan: Smith, Carroll, Dunne, Tighe, Reilly, McEnroe, Graham, Givney (0-1), McKiernan, Smith, McDermott (0-2, one free), Reilly (0-1), Fitzpatrick (0-2), McKiernan (0-3, two frees), McClarey (1-0). Subs: O Minagh (for Carroll), Maloney-Derham 0-1 (for Smith), Smith for (McClarey).
Monaghan: McArdle, Reilly, Daly, Galligan, Hughes, Duffy, Walsh, Hughes (0-1), G McArdle, B McArdle, Malone (0-1), Hahessy (0-3, two frees), McGuinness (0-2, one free), Tavey, Millar (1-0).Subs: O'Hara 0-1 (for G McArdle), McNally 0-1 (for Tavey), G McArdle (for Hahessy); Hill (for Millar).
Referee: McConnell (Fermanagh).