Parental care is widespread across the animal kingdom. Parental behaviours are beneficial by increasing offspring survival but induce significant costs to the parents. Because parental care is much more represented in females, associated reproductive costs have been largely studied in this sex. While male parental care is likely to involve significant costs, it has been markedly less investigated. We studied the costs of egg carrying on locomotor performance in an amphibian species (Alytes obstetricans) with male parental care. We examined complementary parameters including hopping performance, righting-response, hindleg muscles response to egg burden, and homing time in males carrying eggs or not. We found that carrying males had altered locomotor performance for most traits. In addition, alteration of performance was closely related to relative clutch size. Clutch desertion occurred in smaller individuals carrying larger relative clutch mass, and the performance after desertion was similar to that of non-reproductive ones. Overall, our study demonstrates that carrying eggs significantly alters male mobility and that performance-clutch size trade-offs are relevant to understand the evolution of paternal care.