Marine phytoplankton produce essential fatty acids (FA), which are key component of a healthy diet in humans and marine food webs. Increased temperatures can reduce lipid and FA content in phytoplankton; thus, ocean warming poses a risk for the global production of these essential FA. However, responses to warming may differ between phytoplankton species especially after long-term exposure because phenotypic plasticity, de novo mutations or genetic evolution may occur. Here, we examine the content of FA and lipids in phytoplankton following long-term selection (~2 years) to warming conditions (+ 4°C), and we observe that FA and lipids content were partly or entirely recovered following long-term exposure to warming conditions. Furthermore, this observed long-term response also offset the predicted losses of some essential polyunsaturated fatty acids (PUFA) in three of the four species tested. Our study suggests that long-term exposure of phytoplankton to warming may help to maintain marine food quality in a moderately warming ocean. The responses of FA to increasing temperatures may vary among species, and the level of this idiosyncrasy remains to be further studied.