AbstractThe current research investigated whether mothers of transgender youth experience stigma‐by‐association. Mturk participants (N = 489) were randomly assigned to read a vignette about a family in which the social identity (transgender, gay/lesbian, cisgender/heterosexual control) and gender (girl, boy) of a child was manipulated, while all other information was held constant. Results revealed stigma targeting mothers as a function of children's social identity (but not gender), such that mothers of transgender girls and boys were viewed substantially more negatively than identical mothers of cisgender/heterosexual youth. Moreover, this stigma was particularly robust among politically conservative participants. In contrast, mothers of gay/lesbian youth did not encounter systematic stigma, though they were sometimes perceived more negatively than mothers of cisgender/heterosexual youth. Results provide novel experimental evidence of stigma‐by‐association targeting mothers of transgender youth and raise serious concerns about the treatment of parents who seek to affirm their transgender children.