Oceans are changing rapidly and marine organisms must adapt. Epigenetic modifications such as DNA methylation may be an important mechanism underlying fast, adaptive responses, as they can contribute to heritable changes within populations and drive rapid evolution. Crucial during gametogenesis and development (embryogenesis), DNA methylation can be mitotically and/or meiotically heritable, and in some circumstances, can be transgenerationally inherited. However, in order to be inherited, epigenetic mutations must overcome DNA methylation reprogramming which occurs twice, once in the germline and once in the early embryo. But despite being well documented in plant and mammalian systems, methylation studies during fish gametogenesis and embryogenesis have focused mainly on few species. Here, we investigated DNA methylation patterns, together with the molecular characterization and mRNA expression profiles of DNA-methyltransferase enzymes (DNMT), during gametogenesis and embryogenesis of threespine stickleback. Additionally, the impact of multiple simulated ocean warming scenarios (ambient °C, +1.5°C and +4°C) were evaluated at the epigenetic and phenotypic level to establish a functional link between methylomes and transgenerational plasticity, and their role in adaptive potential to climate change.