Background: Studies of schizophrenia have pointed to the role of glutamate in its pathophysiology. Mice lacking D-serine show impairments in neurotransmission through NMDA receptors and display behaviors consistent with features of schizophrenia. Yet, socio-communicative deficits, a characteristic of schizophrenia, have not been reported in serine racemase knockout mice. Methods: We use behavioral testing (the three-chambered social approach task, the dyadic interaction task, and the novel object recognition task) to examine socio-communicative behaviors in these mice. Results: Serine racemase mice show abnormal social investigation and approach behavior, and differ from wild-type controls in the duration and number of vocalizations they emit in the presence of a conspecific. Serine racemase knockout mice were not impaired in a cognitive test (novel object recognition), although they displayed abnormal behavior in the acquisition phase of the task. Conclusions: Serine racemase knockout mice demonstrate abnormalities in socio-communicative behaviors consistent with an impairment in sociality, a negative symptom of schizophrenia.