ROV cables are subjected to various mechanical stresses. This paper investigates the effect of bending fatigue on the dielectric strength of XLPE and polypropylene cable. Single conductors were aged on a bend-over-sheave setup for 5000 and 10000 cycles, and short breakdown tests were performed. Partial discharge (PD) analysis was also done to study the degradation mechanisms underlying the breakdown results. XLPE showed significant degradation with bending fatigue, while polypropylene showed the opposite effect. PD analysis showed that PD magnitude increased with ageing for XLPE and decreased for polypropylene.