Forming accurate perceptions is often linked to positive relationship and individual functioning, yet may also be detrimental in some contexts. The current study examined whether accuracy may be detrimental to individual functioning, both psychological and physiological, in an important social context: parent–adolescent relationships. Specifically, we examined whether the accuracy of adolescents’ perceptions of their parent’s behaviors was associated with adolescent psychological adjustment (depression and perceived stress; N _dyads = 99) and proinflammatory profiles (N _dyads = 95). Adolescents who viewed their parent’s behaviors more accurately (more in line with external observers’ ratings) reported worse psychological adjustment and demonstrated worse regulation of the inflammatory response. In contrast, adolescents who viewed their parent’s behaviors highly normatively and positively reported better psychological adjustment. Overall, these findings suggest that adolescent accuracy regarding parent behaviors may be detrimental to adolescent psychological adjustment and inflammatory processes.