Objective: Cognitive challenges are prominent features of individuals diagnosed with schizophrenia, impairing occupational, social, and economic functioning. These challenges are predictive of social and work outcomes. Cognitive remediation has been shown to be effective in improving both cognitive and social functions. However, cognitive remediation does not produce improvement in all participants. We investigated demographic, neurocognitive, and psychopathological predictors associated with improvement following cognitive remediation interventions in service recipients with severe mental illnesses. Method: One hundred thirty-seven adult participants with a diagnosis of schizophrenia, schizoaffective disorder, or bipolar disorder according to the Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.) were enrolled in 12-week cognitive remediation programs. Assessments of demographic and illness variables, together with baseline and end point assessment of psychopathology (Positive and Negative Syndrome Scale [PANSS]), neurocognition (Measurement and Treatment Research to Improve Cognition in Schizophrenia [MATRICS] Consensus Cognitive Battery [MCBB]), and social functions (Personal and Social Performance Scale [PSP]) were conducted. Change in cognitive domains was calculated using the reliable change index. Logistic regression analysis was used to assess predictors of cognitive improvement after the intervention. Results: Sixty-two percent of participants improved on at least 1 of the MCCB domains. Higher baseline speed of processing, attention or vigilance, and working memory predicted a positive response to cognitive remediation. Younger age, higher education level, shorter length of stay, and lower PANSS Negative and Disorganized factors were additional predictors. Conclusions and Implications for Practice: Our results indicate the clinical usefulness of cognitive remediation and identified a pattern of clinical and cognitive predictors of good response to the intervention. Identification of these predictive factors by clinicians may enhance the outcome and aid in the development of individualized rehabilitative cognitive remediation treatment plans.