We explored parent and adolescent reports of family functioning, how this differed if the parent was aware that their child self‐injured, and how parental awareness of self‐injury was related to self‐injury frequency, self‐injury severity, and help seeking. Participants were 117 parent–adolescent dyads, in 23 of which the adolescent self‐injured. Adolescents who self‐injured reported poorer family functioning than their parents, but parents who did not know about their child's self‐injury reported similar functioning to parents whose children did not self‐injure. Parents were more likely to know that their child self‐injured when the behavior was severe and frequent. Help‐seeking was more likely when parents knew about self‐injury. Family‐based interventions which emphasize perspective‐taking could be used to effectively treat self‐injury.