Most Brazilian yellow scorpion (Tityus serrulatus Lutz & Mello, 1922) populations reproduce by parthenogenesis, and only a few sexually reproducing populations are known. It has been suggested that the parthenogenesis in T. serrulatus is related to bacterial endosymbionts, but this hypothesis was recently refuted, so the causes of parthenogenesis in this species are still unknown. In the present study, we report parthenogenetic reproduction in females from a sexual population, either isolated in laboratory since birth or collected at juvenile stages. Twelve females collected as juveniles became adult and reproduced without contact with males (thus, through parthenogenesis) in the laboratory. Five females collected already pregnant gave birth to litters (F1) composed only of females, which is suggestive of parthenogenesis in the field. Eight F1 females from those litters subsequently reproduced by parthenogenesis in the laboratory. Another female collected already pregnant gave birth to a litter composed of males and females (F1), indicating sexual reproduction in the field. However, one F1 female from that litter reproduced by parthenogenesis in the laboratory. These results suggest that asexual reproduction is facultative in this population.