Objective: To evaluate the prescription patterns and prescribed daily dose (PDD)/defined daily dose (DDD) ratios of antiepileptic drugs (AEDs) in prevalent patients with epilepsy in Taiwan. Materials and methods: A nationwide retrospective cross-sectional study was conducted for prevalent patients with epilepsy in 2016 using the Taiwanese National Health Insurance Research Database. The prescription records of AEDs of all prevalent patients with epilepsy were retrieved. The mean PDDs and PDD/DDD ratios of AEDs in adult patients were obtained to evaluate dosing adequacy. A chi-square test and two-sample t test were used to analyze the differences in AED prescription patterns and dosages, respectively, among patients with different ages, sexes, comorbidities, and therapeutic approaches. Results: A total of 118,937 prevalent patients with epilepsy were enrolled. The predominant therapeutic approach was monotherapy, especially in the elder adults, accounting for 82.9% of elder adult patients with epilepsy. The proportion of AED monotherapy was higher in patients with dementia (78.9%) and stroke (80.6%). The top three antiepileptic monotherapies were valproic acid (28.7%), levetiracetam (19.1%), and phenytoin (16.9%); however, oxcarbazepine (22.8%) was substituted for carbamazepine (3.9%) as monotherapy for patients aged 0–17 years. Among adult patients with epilepsy, the PDD/DDD ratio of each AED in monotherapy was less than 1.00. The mean PDD of each AED was higher in polytherapy than in monotherapy (p < 0.01), except for lacosamide. The mean PDDs of all evaluated AEDs in monotherapy were lower in elder adult patients than in younger adult patients, most of which reached statistical significance (p < 0.001). Conclusions: In Taiwan, valproic acid was the most prescribed AED for prevalent patients with epilepsy. The mean PDDs of most AEDs were lower than the DDDs developed by the World Health Organization.