The purpose of this study was to investigate the validity of the Revised Optimism-Pessimism Scale (PSM-R) as a measure of attributional style, and the incremental utility of optimism and pessimism as predictors of seizure group, in an intractable seizure disorder sample. Participants included adult patients with epileptic seizures (ES; n = 151) and psychogenic nonepileptic seizures (PNES; n = 173) whose diagnoses were confirmed by prolonged video/EEG monitoring (PVEM). Optimism and pessimism scores were computed from abbreviated versions of the MMPI for all participants. Analyses were conducted to examine the relationships between optimism, pessimism, and MMPI clinical scale scores. Logistic regression analyses were conducted to generate a model for the prediction of seizure group. Results supported the validity of the PSM-R as a measure of attributional style in an intractable seizure disorder sample. Both optimism and pessimism provided significant incremental predictive utility over and above other predictors of seizure group. There are advantages of using the proposed prediction model over other alternative differential diagnostic procedures, including lower cost, greater availability, and increased standardization. Overall, results indicated that attributional style is a clinically relevant index of personality and cognitive response to stress among an intractable seizure disorder sample.