Climate change will mediate a rise in seawater temperature and may simultaneously increase the average irradiance conditions in the upper oligotrophic ocean. This could have considerably effects on oceanic ecosystems, since high photosynthetically active radiation (PAR, 400-700 nm) and ultraviolet radiation (UVR, 280-400) may reduce photosynthesis and viability in oceanic picophytoplankton. In the present study, the temperature-dependence of excessive irradiance induced photoinhibition and photoregulation were studied in different oceanic picophytoplankton species. To this end, two prokaryotic strains (Prochlorococcus sp. eMIT9313 and Prochlorococcus marinus eMED4) and two eukaryotic strains (Ostreococcus sp. clade B and Pelagomonas calceolata) were acclimated to three different growth temperatures and exposed to high PAR, with and without UVR. The response to excessive irradiance exposure was assessed by photosystem II (PSII) fluorescence analysis to determine non photochemical quenching (NPQ). Relaxation analyses of NPQ were performed to discriminate photoinhibition and photoprotective processes. In addition, photoprotection was assessed by pigment analysis. Results demonstrated that both the prokaryotic and the eukaryotic picophytoplankton strains were susceptible to photoinhibition. Ostreococcus sp. showed highest levels of photoprotection with an effective de-epoxidation of xanthophyll pigment cycle. Temperature acclimation influenced the response to excessive irradiance exposure by species specific changes in the relative contribution of photoinhibition and photoprotective processes to NPQ. Acclimation to elevated temperatures decreased photoinhibition in P. marinus and P. calceolata, whereas the dissipation of excess energy increased in P. marinus and Prochlorococcus sp.. Elevated temperatures also partially counteracted the UVR-induced PSII photoinhibition in all strains, except Prochlorococcus sp.. Overall, specific picophytoplankton groups have different sensitivities to high PAR and UVR and this may have a significant impact on phytoplankton species distribution and community composition in the open oligotrophic oceans.