Abstract: It is known that the electrochemical determination of phenacetin, a widely used analgesic, is challenging because of the interference of the electroactive intermediate, acetaminophen. Phenacetin was proven to be electroactive in 1980s, but its electrochemical determination has not been widely reported. This determination on an electrochemically reduced graphene oxide (ERGO) electrode was investigated and compared with several nitrogen-doped graphene samples. Results indicate that ERGO has a higher current response and lower oxidation potential than nitrogen-doped graphene. An ERGO electrode as a phenacetin sensor has a detection limit of 0.91 μmol L⁻¹. The redox mechanism of phenacetin is inferred by electrochemical experiments, and the reactions under different pH values are proposed. Acetaminophen is considered to be the main intermediate and that does not interfere with the determination of phenacetin. But phenacetin obviously interferes with the response of acetaminophen, suggesting that the simultaneous detection of phenacetin and acetaminophen is not possible. Species such as Cu²⁺, Al³⁺, methanol, ethylene glycol, glucose, and ascorbic acid do not interfere with the determination of phenacetin.