In this research, the adhesion properties of bonded composite-to-aluminium joints are evaluated using floating roller peel tests. Tests were performed using two different adhesives and different adherend lay-ups: composite-to-aluminium, composite-to-composite and aluminium-to-aluminium. The results show that floating roller peel tests, widely used in metal bonding, can also be used to assess adhesion properties of composite bonding and composite-to-aluminium bonding. However, attention should be paid on which results are important to take from the peel tests. In adhesion tests, the failure mode is more important than the failure load. The peel load can only be compared when using exactly the same type of flexible adherend. Even when the adhesion properties are good (cohesive failure), the peel load value can decrease up to a factor of 10 when peeling off a composite flexible adherend instead of an aluminium flexible adherend.