Background: Research has shown that patients with schizophrenia spectrum disorders (SSD) can be distinguished from controls on the basis of their non-verbal expression. For example, patients with SSD use facial expressions less than normals to invite and sustain social interaction. Here, we sought to examine whether non-verbal expressivity in patients corresponds with their impoverished social competence and neurocognition. Method: Fifty patients with SSD were videotaped during interviews. Non-verbal expressivity was evaluated using the Ethological Coding System for Interviews (ECSI). Social competence was measured using the Social Behaviour Scale and psychopathology was rated using the Positive and Negative Symptom Scale. Neurocognitive variables included measures of IQ, executive functioning, and two mentalising tasks, which tapped into the ability to appreciate mental states of story characters. Results: Non-verbal expressivity was reduced in patients relative to controls. Lack of "prosocial" nonverbal signals was associated with poor social competence and, partially, with impaired understanding of others' minds, but not with non-social cognition or medication. Conclusion: This is the first study to link deficits in non-verbal expressivity to levels of social skills and awareness of others' thoughts and intentions in patients with SSD.