Animals respond to diurnal shifts in their environment with a combination of behavioral, physiological, and molecular changes to synchronize with regularly-timed external cues. The light:dark cycle is regarded as the most important entrainment cue for setting cycles in many bilaterian including mammals, fish, insects and other invertebrates; but the molecular mechanisms that may be responsible for these phenotypes in non-bilaterian phyla remain largely unknown. To improve our understanding of how the photoperiod impacts circadian oscillation in cnidarian organisms (sister group to bilaterians), the sea anemone Nematostella vectensis was used to develop transcriptional and behavioral profiles in response to different light conditions. Nematostella has oscillating patterns of locomotion and respiration, as well as the molecular components of a putative circadian clock that may provide a mechanism for these light-induced responses. Transcriptional profiling revealed large shifts in differential gene expression in response to light removal and to different wavelengths of light. Further, analysis revealed many circadian clock related genes shift expression or lose expression depending on the light cue, suggesting that this repertoire of genes may be photo-responsive rather than truly circadian and behavioral profiling of anemones in different wavelengths revealed a potential circatidal clock in anemones. Our data highlight the importance of diel light cycles on circadian mechanisms in this species, prompting new hypotheses for the role of photoreception in major biological processes, e.g., metabolism, immunity.