We developed microsatellite loci to examine the occurrence of multiple paternity in the praying mantid Tenodera aridifolia Stoll, as inferred from the genotypes of the progeny within field-collected oothecae (egg cases). The microsatellite locus MTA, developed from field-caught mantids, was found to have three alleles (A, B, and C) among >600 hatchlings from 18 oothecae from two locations in Japan. Of the 18 oothecae, two show clear evidence of multiple sires, two show equivocal evidence of multiple sires, and the remaining 14 do not show evidence of multiple sires. Thirteen of the latter 14 oothecae are exclusively homozygous, with all progeny being of the same genotype (BB). Although the exclusively homozygous oothecae suggest a high incidence of monogamy in these field populations, we caution that we probably underestimated the incidence of multiple paternity, given our use of one locus with three alleles. This study is the first genetic investigation of field-collected progeny of a sexually cannibalistic species, as well as the first demonstration of multiple paternity in nature for a sexually cannibalistic species.