In this work, new electrochemical sensors based on the modification of glassy carbon electrode (GCE) with multiwalled carbon nanotubes (MWCNTs)—rare metal oxides (REMO) nanocomposites were fabricated by drop-to-drop method of MWCNTs-REMO dispersion in ethanol. REMO nanoparticles were synthesized by precipitation followed by hydrothermal treatment at 180 °C in absence and presence of TritonTM X-100 surfactant. Cyclic voltammetry (CV) analysis using [email protected] and [email protected] sensors were used for the analysis of sulfisoxazole (SFX) drug in water samples. The results of CV analysis showed that [email protected] sensors have up to 40-fold higher sensitivity with CeO2 compared to the bare GCE sensor. The estimated values of the limit of detection (LoD) of this electrochemical sensing using [email protected] and [email protected] electrodes reached 0.4 and 0.7 μM SFX in phosphate buffer pH = 7, respectively. These findings indicate that [email protected] electrodes are potential sensors for analysis of sulfonamide drugs in water and biological samples.