Clermont beat Toulouse 18-14 in their Top 14 semi-final in Bordeaux to set up a decider against Stade Français.
Toulouse scored the only try of the game through fullback Maxime Médard and led with 10 minutes remaining.
But a late penalty and drop goal from Australian Brock James, who came off the bench, gave Clermont the win.
Clermont will now take on Stade Français, who beat champions Toulon 33-16 in Friday's semi-final.
Clermont – Penalties: Morgan Parra (4), Brock James. Drop goal: James.
Toulouse – Try: Maxime Médard. Penalties: Luke McAlister (3).
Clermont – 15 Nick Abendanon, 14 Aurélien Rougerie, 13 Benson Stanley, 12 Wesley Fofana, 11 Noa Nakaitaci, 10 Camille Lopez, 9 Morgan Parra, 8 Fritz Lee, 7 Julien Bardy, 6 Damien Chouly (c), 5 Sébastien Vahaamahina, 4 Paul Jedrasiak, 3 Davit Zirakashvili, 2 John Ulugia, 1 Thomas Domingo.
Subs: 16 Benjamin Kayser, 17 Raphaël Chaume, 18 Julien Pierre, 19 Alexandre Lapandry, 20 Ludovic Radosavljevic, 21 Brock James, 22 Jean-Marcellin Buttin, 23 Clément Ric.
Toulouse – 15 Maxime Médard, 14 Vincent Clerc, 13 Yann David, 12 Luke McAlister, 11 Yoann Huget, 10 Jean-Marc Doussain, 9 Sébastien Bézy, 8 Gillian Galan, 7 Yannick Nyanga, 6 Thierry Dusautoir (c), 5 Patricio Albacete, 4 Joe Tekori, 3 Census Johnston, 2 Corey Flynn, 1 Gurthö Steenkamp.
Subs: 16 Cyril Baille, 17 Julien Marchand, 18 Yoann Maestri, 19 Louis Picamoles, 20 Toby Flood, 21 Florian Fritz, 22 Timoci Matanavou, 23 Dorian Aldegheri.
Photo: Romain Perrocheau/AFP Photo
