<p>Acyclovir is an important drug that needs to be monitored for accumulation or misuse, especially in people on antiviral therapy. Therefore, it is important to design a sensitive and selective electrode for the determination of acyclovir. In this study, a novel NH₂-functionalized graphene oxide-modified glassy carbon electrode (NH₂-GO/GCE) was developed for the sensitive and accurate determination of acyclovir. NH₂-GO was synthesized by a simple amination method, and the sensor surface was formed by drop-casting it onto the GCE surface. NH₂ groups accelerated electron transfer by the electrochemical response of the modified electrode compared to GO and contributed to stronger interactions with the analyte. In this way, the developed NH₂-GO/GCE sensor showed high sensitivity and selectivity in acyclovir determination. The detection limit was determined as 9.2&#xa0;nmol&#xa0;dm⁻³ and a wide linear range between 0.03 and 500&#xa0;µmol&#xa0;dm⁻³ was obtained. The applicability of the NH₂-GO/GCE sensor was tested on pharmaceutical tablet samples and satisfactory recovery rates were obtained. Furthermore, the developed sensor retained more than 92% of the initial response after 15&#xa0;days and showed relative standard deviation (RSD) values below 4.5%. This demonstrated the storage stability and reproducibility of the sensor.</p> Graphical abstract <p></p>