The Rotter Incomplete Sentences Blank (RISB; Rotter, Lah, & Rafferty, 1992) is a sentence completion test intended to detect psychological maladjustment. To investigate the construct validity of the measure, we investigated what aspects of personality and psychopathology are correlated with the RISB and also tested the incremental validity of the RISB in a combined sample of clinical (n = 72) and undergraduate participants (n = 69). Interrater reliability of the RISB was good (intraclass correlation > .80). The RISB overall adjustment score discriminated between clinical and undergraduate participants, and high scores on the RISB were associated with higher negative affect, more anxiety and depression, irrational thinking, and interpersonal problems. The incremental validity of the RISB was modest, but it did explain variance in satisfaction with life and personality disorder symptoms above and beyond an extracted measure of general psychological distress. Our findings support the construct validity of the RISB.