Our research focuses on identifying lipids involved in the symbiosis between the anemone Aiptasia pallida and its photosynthetic dinoflagellate Symbiodinium. Liquid chromatography quadrupole time‐of‐flight mass spectrometry (MS) was used to analyze lipid extracts of aposymbiotic and holosymbiotic A. pallida and Symbiodinium. By comparing the intensity of each lipid (as defined by RT and m/z) between aposymbionts and holosymbionts, we observed lipidomic changes that occur when A. pallida and Symbiodinium enter symbiosis. The lipidome of A. pallida displays numerous changes as a result of symbiosis formation; [M‐H] − ions at m/z 765.4, 1033.5, and 1061.6 displayed >900‐fold increase in intensity. To begin to characterize these lipids, we partially purified via normal phase HPLC the lipid at m/z 765.4. Using collision induced dissociation MS and chemical modifications of functional groups we hypothesize that the lipid at m/z 765.4 is a diacyl‐glycerosulfolipid, with a head group attached to the sulfate with the formula C6H9O4. This work will lay the foundation for biochemical classification of all of the lipids in this systeme, and determination of what role they play in the symbiosis. This work was funded by a Cottrell College Science Award to J. Schwarz and E. Eberhardt and an ASBMB Undergraduate Affiliate Network Summer Research Award to J. Schmeitzel.