The present study examined the relation between Broad Autism Phenotype (BAP) tendencies and social cognition in mothers who had a child with Autism Spectrum Disorder (ASD) in Japan. The participants of this study were 51 mothers who had a child with ASD. The survey consisted of a questionnaire (BAPQ-J) and four social cognition tasks. The results indicated a cultural difference in “pragmatic language.” Next, those who scored higher on the total BAPQ-J or on the “rigid” subscale had greater difficulty in reading emotions in situations without happy facial cues or surprised facial cues. Additionally, these individuals had greater difficulty with complex judgments, such as judging trustworthiness, from movements and multiple facial stimuli. In summary, BAP and social cognition have some correlation in mothers who have children with ASD.