In this study, a sensitive electrochemical sensor for chlorpromazine was established based on La3+/Co3O4 nanoflower. The La3+/Co3O4 nanoflower exhibited superior electrochemical activity towards the oxidation of chlorpromazine. Electrochemical oxidation of chlorpromazine on the modified electrode was an diffusion-controlled process. Electrochemical oxidation peak currents linearly increased with chlor-promazine concentrations in the range of 0.5 and 400.0 μM. The detection limit was calculated as 0.08 μM. The La3+/Co3O4/GCE allowed to determine the chlorpromazine in real samples. The results indicated that the electrochemical sensor prepared in this study could be a very promising alternative to current analytical methods used to determine chlorpromazine.