--- - |2 This study's aim was to apply a Contextual theory lens on exploring whether knowledge of parental infidelity affects the Relational Ethics (RE) of adult children. The Relational Ethics Scale (RES) was used to capture horizontal (partner) and vertical (family of origin) relational ethics in a clinical sample of 195 participants. A repeated measures ANOVA tested the differences in RES scores among the participants who reported knowledge of parental infidelity and the participants who did not. Results showed that knowledge of parental infidelity is significantly associated with lower scores on the RES, which indicates problematic relationships, both in partners and with family of origin. Clinical implications on how parental infidelity can affect relational ethics are discussed. - Journal of Marital and Family Therapy, EarlyView.