We examined the seasonality of reproduction in captive and wild bottlenose dolphins, Tursiops truncatus. Stranding records of neonatal dolphins and observed births from a long-term field study were used to estimate peak periods of birth for wild populations, and information from captive-breeding colonies was used to assess the effects of latitude and origin of breeding females on timing of birth for dolphins in captivity. Bottlenose dolphins showed diffuse peaks and considerable flexibility in their seasonality of reproduction. There was no relationship between latitude and seasonality of reproduction or synchrony of births. However, there was a correlation between origin of population and seasonality of reproduction in both wild and captive dolphins. We suggest that adaptations to local environmental conditions have the strongest influence on seasonality of reproduction in these populations of bottlenose dolphins.