The study of social cognition (SC) has emerged as a key domain of mental health, supporting the notion that poorer performance in SC tasks is linked to psychopathology, although most studies have primarily addressed only schizophrenia (SZ). Some recent studies have also shown deficits of SC in obsessive-compulsive disorder (OCD) patients; however, little is known about how individuals with OCD may differ on SC performance from individuals with SZ. Moreover, initial research in this field suggests that mindfulness skills may be related to SC abilities such as theory of mind (ToM), emotion processing and empathy. Given the potential benefits of mindfulness for treating OCD and SZ, further efforts are needed to understand the association between mindfulness and SC in these populations. The main objective of this study was to compare samples of patients with SZ and OCD to healthy controls (HCs) on several social cognition (SC) domains and mindfulness measures. In total, 30 outpatients diagnosed with SZ, 31 outpatients diagnosed with OCD and 30 healthy controls were assessed in emotion recognition (the Eyes Test), ToM (the Hinting Task), attributional style (the Ambiguous Intentions and Hostility Questionnaire), empathy (the Interpersonal Reactivity Index) and dispositional mindfulness (the MAAS and the FFMQ). Both clinical groups showed poorer performance in emotion recognition and ToM than the HCs. The OCD and SZ patients did not significantly differ in impairment in SC, but the OCD group had higher scores in attributional style (intentionality and anger bias). With regard to mindfulness, the results found lower levels of acting with awareness for the HCs than for either clinical group and higher non-reactivity to inner experience for the HCs than for the individuals with OCD; the results also yielded significant correlations between SC and mindfulness. In conclusion, these findings revealed that SC abilities were impaired in the SZ and OCD groups compared to the HC group, suggesting a similar disrupted pattern in both clinical groups. Aspects of dispositional mindfulness were differentially associated with SC, which may suggest their potential role in novel transdiagnostic interventions.