Among haplorhine primates, the highly specialized Callitrichidae (marmosets and tamarins) are expected to have comparatively high reproductive costs, a feature that might be related to the evolution of a cooperative breeding system. Costs of reproduction in captivity were investigated on the basis of changes in energy intake and body weight during pregnancy and lactation in pair-living female and male common marmosets (Callithrix jacchus). The experimental design had little effect on carrying behavior, food intake, and body weight of adults, but a negative transitory effect of offspring body weight. Increased energetic requirements during pregnancy did not result in a higher energy intake in females. During lactation, females increased their energy intake up to 100% and gradually lost weight, suggesting even higher costs. Extensive carrying behavior by males, on the other hand, did not result in an increased energy intake in males, or in changes in male body weight. It is suggested that, at least in captivity, increased energetic demands during reproduction are reduced by behavior allocations towards energetically less expensive behaviors.