Acetaminophen (AAP), which is also known as paracetamol, is a widely available over-the-counter medication and is a leading cause of poisoning worldwide. Improper disposal of the residues generated during the manufacturing process of this medicine will end up polluting water bodies, causing significant harm to the environment. Therefore, it is crucial to frequently and accurately monitor the presence of such medications. This paper reports the fabrication and characterization of an inexpensive sensor to detect AAP. To enable the detection, this sensor utilizes the electrochemical behavior of AAP on Au nanoparticles. Herein, Au is deposited over the ITO-PET sheet using the electrodeposition method. Cyclic voltammograms of AAP with Au exhibited well-defined redox peaks. Under the optimum pH of 13 in 0.1 M NaOH, the material showed a linear response within the concentration range of 6–80 nM of AAP (with R \(^2\) = 0.971). The detection limit was estimated to be 430 picomolar (pM) with a sensitivity of 0.76 microAmp/nM. The sensor is fabricated on an inexpensive substrate with a non-CMOS fabrication process, which makes the sensor economical.