Multiple paternity within clutches has been recorded among a variety of organisms. The degree of genetic similarity between parents may influence the number and viability of offspring. Females may therefore mate with several males as an insurance against sterile, low quality or genetically incompatible mates, but also to obtain half sibling offspring that are genetically and phenotypically more diverse. We examine the links between polyandry, multiple paternity and offspring phenotypic diversity in the color polymorphic pygmy grasshopper Tetrix subulata. By experimentally mating virgin females and genotyping the resulting offspring using microsatellite markers, we demonstrate that polyandrous females can produce offspring sired by different males. Analyses of microsatellite data and color patterns of captive reared families produced by wild caught females that were not mated in the laboratory, confirmed that multiple paternity occurs in the wild, and that it may increase color morph diversity among half-siblings. Polyandrous mating behavior may thus influence the evolutionary dynamics and maintenance of color polymorphism in this species.