The Blues, who were led by Welsh winger Rhys Williams, ran in five tries in Brescia on Sunday afternoon, scoring a 38-9 defeat over third-ranked Italians Viadana to qualify for next season's top-tier tournament.
Cardiff claimed their play-off place as the highest-placed non-qualifying team in the Celtic League, beating off the challenge of tenth-placed Connacht by just three league points.
Clermont Auvergne, meanwhile, who boast Wales and Lions fly-half Stephen Jones in their ranks, clinched the seventh French place when they triumphed 31-8 in a Top 16 head-to-head with Agen at Stade Marcel-Michelin.
Rugby Calvisano took Italy's number one seed ranking for the 2005/06 Heineken Cup, by virtue of their 25-20 Super 12 Italian Championship final win over Benetton Treviso.
2005/06 Heineken Cup Confirmed Qualifiers:
FRANCE (7): (Top 4 rankings to be decided) Biarritz Olympique, Bourgoin, Stade Francais, Toulouse; Perpignan, Castres Olympique, Clermont Auvergne.
IRELAND (3): Munster, Leinster, Ulster.
ITALY (2): Rugby Calvisano, Benetton Treviso.
SCOTLAND (2): Glasgow Rugby, Edinburgh Rugby.
WALES (4): The Ospreys, Newport-Gwent Dragons, Llanelli Scarlets, Cardiff Blues.