Acetaminophen (Ac) is a pharmaceutically active ingredient widely used in the treatment of pain and fever. However, an acute oral overdose of more than 12 g of Ac is considered a toxic dose and poses a high risk of liver damage. This study presents the development of a new laboratory-made screen-printed electrode modified with reduced graphene oxide (rGO)-subphthalocyanine-functionalized with ferrocene (SubPc-Fc) to detect Ac. Initially, subphthalocyanine (SubPc) was synthesized using a known method from the literature and was then functionalized with ferrocene (Fc). Subsequently, this functionalized compound was combined with rGO to form a composite structure (rGO–SubPc-Fc). A laboratory-made screen-printing electrode (LabSPE) was successfully created by using carbon and silver conductive inks applied to a polycarbonate substrate through the screen-printing process. Then, the surface of LabSPE was modified with rGO–SubPc-Fc composite and made ready for the electrochemical determination of Ac. The electrochemical results revealed that the rGO–SubPc-Fc composite exhibited a remarkable sensing behavior towards the oxidation of Ac with a working range from 0.05 μM to 200 μM, and a detection limit of 0.01 μM. The selectivity of the proposed sensor (rGO–SubPc-Fc/LabSPE) for Ac detection in the presence of possible interfering compounds such as uric acid, epinephrine, ascorbic acid, dopamine, and some ions was also examined. The practical suitability of rGO–SubPc-Fc/LabSPE in real sample analysis was tested on two different types of human drug samples and appreciable recovery results were obtained in the range of 102.02–103.94 %. In drug sample analysis, the proposed method was compared with the spectrophotometric method, and satisfactory results were achieved.