Objective The aim of this study was to characterize the neuropsychological features of a representative sample of Sleep-related Hypermotor Epilepsy (SHE) patients and to highlight clinical associations. Methods This cross-sectional study included 60 consecutive patients with video/video-electroencephalography–documented SHE. All were assessed by measures of intelligence. Individuals with normal scores underwent a standardized battery of tests. The Fisher exact test and Wilcoxon rank-sum test for statistical analysis. Results Mean total IQ was 96.96 ± 21.50, with significant differences between verbal and performance scores (p < 0.0001). Nine patients (15%) had intellectual disability (ID)/cognitive deterioration. Of the 49 assessed by the extensive battery, 23 (46.9%) showed deficits in at least one test evaluating phonemic fluency (24.5%), memory (24.5%), inhibitory control (22.4%), or working memory (10.2%). Patients with mutations in SHE genes had lower IQ than patients without mutations, irrespective of the specific gene (p = 0.0176). Similarly, pathological neurological examination (NE) and “any underlying brain disorder” (at least one among pathological NE, abnormal brain magnetic resonance imaging findings, perinatal insult) were associated with ID (p = 0.029, p = 0.036). A higher seizure frequency at last assessment and poor prognosis correlated with worse scores in visuo-spatial memory (p = 0.038, p = 0.040) and visuo-spatial abilities (p = 0.016). Status epilepticus (p = 0.035), poor response to antiepileptic drugs (p = 0.033), and poor prognosis (p = 0.020) correlated with lower shifting abilities, whereas bilateral convulsive seizures correlated with worse working memory (p = 0.049). Conclusion In all, 53.3% of SHE patients had neuropsychological deficits. The profile of impairment showed worse verbal IQ, as well as deficits in extrafrontal and selective frontal functions. Our data support the contribution of genetics in ID by different biological mechanisms. Variables of clinical severity affect memory and executive functioning.