The diapause generation of multivoltine insects requires additional energy reserves for diapause maintenance compared with the nondiapause generation. This requirement suggests that the cost of diapause has an effect on life-history traits. We investigated diapause costs in a multivoltine bruchid, Acanthoscelides pallidipennis Motschulsky (Coleoptera: Bruchidae). In the laboratory, life-history traits of A. pallidipennis were compared between nondiapause and diapause treatments. Fecundity and body size of adults were reduced in the diapause treatment compared with the nondiapause treatment. Larger females laid more eggs than smaller females in both treatments. The reduced fecundity of diapause females likely was caused by their reduced body size as a limiting factor. Our findings support the hypothesis that the cost of diapause results in a difference in life-history traits between nondiapause and diapause generations.