People tend to perceive the self as static and permanent and often use social roles to conceptualize the self. Once created, people are motivated to maintain existing self-concepts. Although psychologists have identified healthy aspects of a conceptualized self (e.g., self-esteem), a fluid, impermanent sense of self is associated with optimized psychological functioning. The Selfing Scale is an 18-item measure that assesses the extent to which one over-identifies with their social roles. The Selfing Scale was developed using both classical and Rasch methodology with a large sample size (n = 1882) establishing high reliability, internal validity, and test-retest validity. Results indicate that selfing is positively correlated with self-worth, self-esteem, self-concept clarity, and self-consciousness, as well as neuroticism, worry, and stress-related symptoms. In addition, greater dispositional mindfulness and greater frequency of mediation are associated with less selfing. These results suggest that greater identification with social roles serves to provide a more defined sense of self, but also results in negative psychological outcomes. Overall, the Selfing Scale is a reliable and valid tool to assess excessive identification with social roles.