Latar Belakang: Epilepsi adalah gangguan susunan saraf pusat yang ditandai bangkitan spontan berulang. Salah satu faktor yang dapat memengaruhi fungsi kognitif pasien epilepsi adalah usia saat onset. Tujuan: Mengetahui hubungan antara usia saat onset dan fungsi kognitif pasien epilepsi di Poliklinik Saraf RSUD dr.Soedarso Pontianak. Metode: Penelitian analitik observasional cross-sectional. Subjek penelitian berjumlah 36 orang. Variabel bebas penelitian adalah usia pasien saat didiagnosis epilepsi, sedangkan variabel terikat adalah fungsi kognitif pasien epilepsi. Hasil: Distribusi pasien epilepsi terbanyak pada golongan usia dewasa muda (usia 18-25 tahun; 30,5%), laki-laki (55,6%), tingkat pendidikan terakhir SMA (44,4%), tidak bekerja (50%), dan belum menikah (52,8%). Kebanyakan onset epilepsi pada usia 19-60 tahun (58,3%), dengan frekuensi bangkitan tidak sering (75%). Sebagian besar pasien teratur minum obat anti-epilepsi (77,8%) dan telah didiagnosis epilepsi selama 15-30 tahun (44,4%). Sebanyak 9 (25%) pasien epilepsi mengalami penurunan fungsi kognitif yang nyata dan 17 orang (47,2%) kemungkinan (probable) mengalami penurunan fungsi kognitif. Uji korelasi Kendal tau menghasilkan adanya hubungan antara usia saat onset dan fungsi kognitif (p<0,004). Simpulan: Terdapat hubungan antara usia onset dan fungsi kognitif pada pasien epilepsi di Poliklinik Saraf RSUD dr. Soedarso kota Pontianak. Background: Epilepsy is a central nervous system disorder characterized by spontaneous recurrent seizures. Age at onset is one of the factors that may influence cognitive function in epilepsy patients. Aim: To search the relationship between the age at onset and cognitive function among epilepsy patients in the Neurology Polyclinic, dr. Soedarso Regional Hospital, Pontianak City, Indonesia. Methods: An analytic observational study with a cross-sectional method. The total subjects were 36 patients. The independent variable was the age of patients at diagnosis, and the dependent variable was cognitive function. Results: Most epilepsy patients were in young adult age (18-25 years; 30.5%), male (55.6%), with high school as the highest level of education (44.4%), unemployed (50%), and not married (52.8%). The onset of epilepsy is mostly at 19 to 60 years old (58.3%), with infrequent seizure frequency (75%). Most patients are regularly taking anti-epileptic drugs (77.8%), and have been diagnosed for 15-30 years (44.4%). A total of 9 (25%) patients experienced a marked decline in cognitive function, and 17 people (47.2%) experienced a probable decline in cognitive function. Kendal tau correlation test resulted in a relationship between the age at onset and cognitive function (p<0.004). Conclusion: There is a relation between the age at onset and cognitive function among epilepsy patients in dr. Soedarso Regional Hospital of Pontianak City.