Background: Social cognitive deficits play an important role in social functioning in adults with established psychosis (schizophrenia), young adults recently diagnosed with schizophrenia in the last 2 years (first episode psychosis; FEP), and teenagers at clinical high risk for developing psychosis (CHR). In particular, the ability to infer other people’s mental states has been shown to be compromised in those with psychosis, albeit less so in earlier stages. Recent studies have shown that processing speed (PS) may be upstream to social cognitive abilities in psychosis. If such were the case, remediating PS may in turn have beneficial effects on social cognition. This study examined whether improving PS would lead to subsequent improvements in social cognition in individuals with schizophrenia, FEP, and/or CHR. We examined whether (a) improving PS was related to improvements in social cognition, and (b) if so, whether these social cognitive improvements would in turn lead to fewer symptoms and better social function.