Toulon had edged 13-6 ahead with a try from Sonny Bill Williams and eight points from Jonny Wilkinson when the Blues mounted their second-half comeback.
But with Wilkinson hobbling off injured on 49 minutes, the Blues roared into life, Jamie Roberts, Leigh Halfpenny and Bradley Davies scoring the tries as the Blues silenced the vast majority of the record 49,996 crowd inside Marseille’s Stade Velodrome.
The result will also be hailed in Llanelli because the Blues’ victory guaranteed the Scarlets Heineken Cup qualification.
Scorers for Toulon: Williams, Sourice try each; Wilkinson con, 2 pens; May pen.
Scorers for Cardiff Blues: Roberts, Davies try each; Blair 2 cons, 2 pens; Halfpenny try, pen.
CARDIFF BLUES: Blair, Halfpenny, Laulala, Roberts, Czekaj, Sweeney, Rees, Jenkins, Thomas, Filise, Davies, Jones, Molitika, M. Williams, Rush.
Replacements: Hewitt for Laulala (80), Yapp for Jenkins (40), G. Williams for Thomas (46), Andrews for Filise (56), Tito for Jones (51), Warburton for Molitika (62). Not Used: Allinson, Flanagan.
TOULON: Marienval, Lovobalavu, May, Williams, Sinzelle, Wilkinson, Henjak, Taumoepeau, Fitzgerald, Kubriashvili, Lozada, Skeate, van Niekerk, Fernandez Lobbe, Auelua.
Replacements: Umaga for Sinzelle (70), Kefu for Wilkinson (46), Mignoni for Henjak (56), Emmanuelli for Taumoepeau (56), Bruno for Fitzgerald (34), Ryan for Kubriashvili (40), Suta for Lozada (51), Sourice for Auelua (68).
Referee: A Rolland (Ireland).