Psychological mindedness (PM) is an underinvestigated, but important construct in psychoanalytic psychotherapy research and practice. It refers to the interest in and ability for reflecting on one's thoughts and feelings, and it represents an important precondition for insight-oriented therapy to be successful. Notwithstanding, very few instruments are available to measure PM. The current investigation aimed at evaluating the validity and reliability of the Balanced Index of Psychological Mindedness (BIPM; NyklíČek & Denollet, 2009, Psychological Assessment, 21, 32–44), a brief measure of PM. In a first study, factor structure, internal consistency, and concurrent validity of the BIPM were tested, along with the relationship between the BIPM and a continuous measure of general distress, using a sample of 298 Italian students. In a second study, test-retest stability analyses were completed using a new, different, Italian student sample (N = 58). In a third study, the BIPM scores of a clinical sample with diagnosis of mood spectrum disorders (N = 30) were compared to those of an age-, gender-, and education-matched nonclinical sample. Overall, results indicate that the BIPM is a psychometrically sound instrument that can be used in clinical practice to obtain rapid information about the client's mentalization skills and assess PM.