The main goal of the current study was to empirically study one of the central constructs in Kohut's self-psychology—self-fragmentation. For this purpose, we constructed a new self-report scale (the Fragmented Self Inventory [FSI]) tapping fragmentations along each of the two major axes of the self—grandiosity and idealization. Across six independent samples, findings provided solid evidence on the reliability and two-factor structure of the scale. In addition, FSI scores were associated with existing scales tapping disorders of the self, self-confusion, frustration of self-object needs, pathological forms of narcissism, interpersonal difficulties, dissociative states, and impoverished mental health. Moreover, the findings of Studies 4-6 provided initial support for the incremental validity of the new scale. FSI scores made a unique contribution to pathological narcissism, mental dissociation, and mental health problems beyond the significant contribution made by existing scales. Findings were discussed from the perspective of Kohut self-psychology.