Background <p>This study was conducted to assess the psychometric soundness of the short form of the Inventory of Parent and Peer Attachment (IPPA-45) and its relationship with internalizing and externalizing behavior problems.</p> Methods <p>Iranian adolescent girls and boys aged 14–17 (<i>n</i> = 1532; 50% girls; Mean _age = 15.50, SD = .97) were asked to report their attachment security, internalizing and externalizing behavior problems (Youth Self-Report), and demographic characteristics.</p> Results <p>Results of the confirmatory factor analysis supported the original three-factor first-order model for maternal, paternal, and peer forms, with equivalency across gender and reasonable reliability. Internal construct validity was supported by acceptable correlation coefficients among the three dimensions. The trust and communication subscales of the IPPA-45 were negatively correlated with all subscales of behavioral problems and adolescents’ age, while positively correlated with academic performance. Conversely, the alienation subscale showed significant but weaker correlations with these variables in the opposite direction. Satisfactory discriminant validity was demonstrated through Average Variance Extracted (AVE) for trust and communication, but not for alienation. Gender discrepancies were observed, with boys exhibiting higher attachment security to their parents and girls displaying stronger attachment to their peers.</p> Conclusions <p>The findings suggest that the IPPA-45 is a reliable and valid instrument for assessing adolescents’ attachments to their parents and peers. Thus, attachment relationships, including peer attachment, appear to be essential for protecting teenagers from behavior problems and should be targeted in intervention programs.</p>