Objective Despite a growing number of studies reporting patients with a history of mania without depression have several socio-demographic and clinical differences than bipolar disorder patients, unipolar mania is recognized as bipolar I disorder in the most commonly used classification systems. Studies showing that unipolar mania is a separate clinical entity are insufficient in number, and to the best of our knowledge, there has been no study investigating the neuropsychological differences in this area. The aim of this study is to evaluate the neurocognitive differences between unipolar mania, bipolar I disorder and healthy controls, and to reveal the underlying neurocognitive differences. Materials and Methods Cambridge Neuropsychological Test Automated Battery was applied to 18 unipolar mania, 19 bipolar I disorder patients and 21 healthy controls matched for age, sex and education levels. Results Unipolar mania group had worse performance regarding visual memory and executive functions, and had specific social cognition deficits compared to both bipolar I disorder and healthy control groups. Conclusion The results of our study indicate that unipolar mania might have unique neurocognitive differences compared to bipolar I disorder, which might support the hypothesis that unipolar mania is a distinct neurocognitive disorder within bipolar spectrum disorders.