Pollen as one of the most important supplementary food benefits the generalist predators in many aspects. However, little is known about the performance of generalist predators with type IV lifestyle when they are reared continuously on prey supplemented with pollen for many generations. In this study, the life history traits of the predatory mites Euseius nicholsi (Ehara et Lee) (Acari: Phytoseiidae) were compared when two prey species, Tetranychus urticae Koch (Acari: Tetranychidae) and Eotetranychus kanktus Ehara (Acari: Tetranychidae) were offered with the presence/absence of camellia pollen. The results showed that the mixed diet of prey and pollen significantly improved the fitness of predatory mites. Predatory mites with pollen as supplementary food developed 1 day faster than their counterparts fed only with prey. They survived much longer and produced almost twice as many eggs as their counterparts. Nevertheless, these benefits were only evident in the first few generations and faded away from Generation 5. This study advanced our understanding by indicating that the beneficial effects of supplementary pollen decreased along with generations and clarifying that T. urticae was a more nutritious prey to E. nicholsi.