Flowering phenology can strongly affect reproductive success. In mass-flowering species, synchronous individuals may have a reproductive advantage because of the increased number of pollinators and decreased probability of predispersal seed predation. We investigated flowering phenology in relation to female reproductive success, and the responses of pollinators and predispersal seed predators to flowering variation, in 4 populations of Sorbus aucuparia in the northwest Iberian Peninsula, 2 of them over a 3-y period. Flowering lasted about 2 weeks at the end of spring, during which most individuals in the populations flowered synchronously (i.e., exhibited mass-flowering). Variation among individuals and populations in flowering dates and flowering duration was significant, and the differences remained consistent between years, especially between those with greater production of flowers and fruits. Pollinator visit frequency was independent of flowering phenology. The relationship between flowering phenology and predispersal seed predation was not significant as well. Contrary to the general hypothesis for mass-flowering, plants flowering earlier showed lower seed predation rates and higher female reproductive success (i.e., greater total dispersed fruits). The selective pressure exerted on flowering phenology by predispersal seed predators may be limited by the effect of plant size on flowering phenology. Plant size and local conditions are important factors affecting phenology and female reproductive success, and they may explain the observed variation in flowering phenology.