Based on clinical evidence and theoretical writings on pathological forms of concern and the destructive role they might play in close relationships, we conducted 2 studies aimed at developing and validating the Pathological Concern Questionnaire (PCQ). This scale comprises items tapping a fragile view of the self, as well as a compulsive need to care for others. Findings indicated that all questionnaire items loaded on a single factor of pathological concern, which was significantly associated with egocentric motivations, attachment insecurities, imbalanced forms of relational entitlement, low self-esteem, low life satisfaction, and negative emotionality. In addition, the PCQ was found to tap a unique psychological construct that differs from constructs of healthy concern and unmitigated communion. The discussion focuses on the developmental and psychodynamic sources of pathological concern as well as its significance in the intrapersonal and interpersonal domains.