Diminished expression is a diagnostic feature of a range of schizophrenia-spectrum disorders/conditions and is often unresponsive to treatment, is present across premorbid, first episode and various clinical states, and is considered a poor prognostic indicator. Surprisingly, little is known about diminished expression. The present study sought to address this issue by evaluating a commercially-available computerized facial analysis software for understanding diminished expressivity. We analyzed natural facial expression from a series of laboratory interaction tasks in 28 individuals with psychometric schizotypy — defined as the personality organization reflecting a putative genetic schizophrenia liability, and 26 matched controls. We evaluated (a) feasibility — defined in terms of the number of video frames recognized by the software, (b) reliability — defined in terms of correlations between facial expression variables across the three laboratory interactions, and (c) construct validity — defined in terms of relationships to clinical variables. For most subjects (~80%), approximately three-quarters of the video frames were analyzable by the software; however, a minority of the videos were essentially unreadable. The facial expression variables showed excellent reliability across interaction conditions. In terms of construct validity, facial expression variables were significantly related to a measure of psychoticism, tapping subjective cognitive concerns and “first-rank” schizophrenia symptoms, but were generally not different between groups. Facial expression variables were generally not significantly related to measures of depression, anxiety, paranoia or, surprisingly, self-reported negative schizotypy. While computerized facial analysis appears to be a reliable and promising method of understanding diminished expressivity across the schizophrenia-spectrum, some work remains. Implications are discussed.