Due to the global decline in sea urchin fisheries, there has been an increased need to produce nutritionally-complete sea urchin diets for the emerging sea urchin aquaculture industry. Previous studies have established various macronutrient requirements; however, micronutrient requirements have not been well-researched in sea urchins. Vitamins are important micronutrients in both vertebrates and invertebrates, but their importance has not been established in any sea urchin species. To establish the essentiality and nutritional requirements of vitamins in sea urchins, a suite of important vitamins were tested in nutritional trials in the sea urchin, Lytechinus variegatus. Sea urchins fed moderate levels of a standard vitamin premix in the diet (0.6% dry weight) had significantly higher (p<0.05) weight gain and organ production than those fed diets with more or fewer vitamins, indicating the essentiality and potential toxicity of vitamins in sea urchins. Juvenile sea urchins fed dietary ascorbic acid (ascorbyl-polyphosphate) had higher weight gain and organ production when fed higher levels of ascorbic acid (>100 mg ascorbic acid/kg diet), suggesting that ascorbic acid may be essential in post-metamorphic growth. Ascorbic acid also promoted a firmer test in adult sea urchins, and also resulted in an increased organic content. However, the biochemical form of ascorbic acid (endogenous ascorbic acid or stabilized ascorbyl-polyphosphate) significantly affected weight gain and organ production in adult sea urchins. Supplementation of dietary alpha-tocopherol did not significantly affect production of small L. variegatus, suggesting that other antioxidants can replace any observed effects of alpha-tocopherol on growth. Lastly, high levels of dietary cholecalciferol did not affect survival, and there was no apparent pathology, suggesting a protective mechanism similar to vertebrates. Although specific vitamin requirements were not established, several vitamins have significant effects on weight gain, organ production, and the quality of the organs in L. variegatus. These studies suggest that vitamin nutritional requirements in sea urchins may vary based on biochemical form of the vitamin, life stage of the sea urchin, and other antioxidants in the prepared diet.