Background/Objectives: Epilepsy is characterized by recurrent, unprovoked, self-limiting seizures of genetic, acquired, or unknown origin. It affects more than 50 million people worldwide. The prevalence in Peru is 11.9–32.1 per 1000 people. Our objective was to describe the association between CYP2C9 and CYP2C19 genetic polymorphisms and adverse reactions induced by antiseizure medications among Peruvian patients with epilepsy. Methods: A descriptive observational study was conducted on Peruvian patients with epilepsy. Non-probability, non-randomized, purposive sampling was carried out through consecutive inclusion. Genomic DNA was obtained from venous blood samples. Genotypes were determined by real-time PCR using specific TaqMan probes to identify the alleles of interest. Results: In total, 89 Peruvian patients with epilepsy were recruited at the Alberto Sabogal Sologuren National H...