We examined feeding by the mangrove tree crab Aratus pisonii in Tampa Bay, Florida, in relation to the percent dry weight of carbohydrate, protein, phenolics, condensed tannins, ash, carbon, nitrogen, carbon:nitrogen ratio, water content, and sclerophylly for leaves of the red mangrove Rhizophora mangle. Comparisons of leaf chemistry were made among leaves that experienced variable levels of crab damage. Because R. mangle is the crab's preferred food source based on damage patterns in the field, comparisons of R. mangle leaf chemistry were made in relation to that of the black mangrove Avicennia germinans and the white mangrove Laguncularia racemosa. We observed a negative relationship between level of leaf damage and percent dry weight of nitrogen, carbohydrates, condensed tannins, and sclerophylly. In contrast, a positive relationship was found between leaf damage and the carbon:nitrogen ratio. The chemical constituents that provided the best explanation for differences in damage among the three mangrove species include condensed tannins, nitrogen, carbon:nitrogen ratio, carbohydrates, phenolics, water content, and ash. The results from this study suggest that chemistry only partially explains food preference by A. pisonii. It appears that A. pisonii feeding behavior and preference may be influenced by a more complex series of factors and interactions, which may include reproduction by, predation on, and interspecific competition with A. pisonii.