ABSTRACT: Reproductive phenology is a crucial life-history trait that is influenced by both environmental and frequency-dependent effects. The fitness benefits of any phenology strategy will depend strongly on other aspects of the life history: one of the most fundamental ways life histories can differ is fertilization mode. Despite the strong potential for fertilization mode to alter selection on phenology, explorations into how these 2 fundamental life-history traits interact are lacking. We explore theoretically how frequency-dependent effects and fertilization mode influence the evolution of asynchronous reproduction, and the evolutionary stable strategy (ESS) for a population in which individuals’ mean and variance in phenology are evolvable traits. We find that when males compete for fertilizations, perfect reproductive synchrony with optimal environmental conditions is never an optimal evolutionary strategy, and asynchronous reproduction is an inevitable consequence of frequency-dependent selection. Fertilization mode qualitatively alters frequency-dependent selection on the variance in phenology, as well as the prevalence of sexual conflict over reproductive timing. Our results contrast with traditional hypotheses that have primarily considered asynchronous reproduction as an adaptive bet-hedging strategy in stochastic environments, and provide a much-needed explanation for the emerging picture of reproductive asynchrony observed in many systems.