Species’ arrival order can determine the structure of communities through priority effects. Despite well-known ecological processes underpinning this phenomenon, it remains unclear how the strength and timescale of evolutionary processes compare. We investigated the strength of ecological and evolutionary priority effects using a Drosophila-parasitoid model system where one of two Drosophila hosts were attacked by two generalist parasitoids arriving in different orders. We found that evolutionary priority effects were generated within a few host generations, whereby first-arriving parasitoids benefitted late-arriving species by inducing heritable changes in host resistance against parasitism, making them more vulnerable to late-arriving hosts. Evolutionary priority effects on parasitism and resistance rates were stronger than ecological effects via host exploitation, highlighting the importance of this overlooked mechanism for shaping communities.