Literature on the association between arachnoid cysts and seizures/epilepsy is inconsistent, and most series have been flawed due to recruitment bias. In this study, we aimed to assess the prevalence of supratentorial arachnoid cysts (SACs) in Atahualpa residents aged ≥20 years, and to estimate whether these lesions were associated with seizures/epilepsy. A total of 1157 individuals were included. Computed tomography revealed SACs in 25 individuals (2.2%). Most had middle cranial fossa SACs (n = 19). Recurrent nonprovoked seizures were diagnosed in 28 individuals and a single seizure in 4. Only 1 of 25 (4%) individuals with SACs had seizures/epilepsy as opposed to 31 of 1132 (2.7%) who did not have SACs (P = 0.508). A logistic regression model showed no association between SACs and seizures/epilepsy, after taking into account the effect of relevant confounders (odds ratio [OR] 1.71; 95% confidence interval [95% CI] 0.22‐13.3; P = 0.607). This study provides evidence of lack of association between SACs and seizures/epilepsy.