Black lemurs, Eulemur macaco, are classified as generalist feeders, consuming a proportion of fruits and leaves that varies with seasonal availability. It is hypothesized that black lemurs are capable of using neutral detergent fiber (NDF) as a source of energy through fiber fermentation in the cecum and large intestine. In captivity, they are typically fed a diet of commercially available primate biscuits and readily available produce, both of which are limited in NDF. Digestibility trials were conducted on 14 black lemurs; 12 were housed in groups (four, three, three, and two) and 2 were individually housed. The lemurs were fed four manufactured feeds differing in fiber form and content. A commercially available primate biscuit, containing approximately 27% NDF, served as the control diet. The second diet contained the same primate biscuits, which were ground and then incorporated into a fiber-based gel matrix. The third and fourth diets were formulated using soybean hulls or ground corncobs as the fiber source, resulting in 53% and 47% NDF, respectively. Produce was added to the diet at 36% (dry matter basis). Dry matter digestibility differed significantly among all diets. Neutral detergent fiber digestibility was highest for the ground biscuit in gel and lowest for the two high-fiber gel diets, with biscuit digestibility values falling between the two extremes. The high-fiber gel diets were successful in increasing the NDF concentrations of the primate diets; however, black lemurs were capable of only limited fiber digestion.