Fastener free metal–carbon fibre reinforced thermoplastic composite hybrid joints show potential for application in aerospace structures. The strength of the metal–thermoplastic composite interface is crucial for the performance of the entire hybrid joint. Optimisation of the interface requires an evaluation method for these hybrid structures. This work demonstrates the applicability of a mandrel peel test method for this purpose. The suitability of the mandrel peel test for certain hybrid joints is evaluated. Furthermore, a series of parameters in mandrel peel test are assessed in order to optimise the evaluation of the performance of metal–thermoplastic interface.