This study describes the fabrication of a novel electrochemical sensor for the simultaneous determination of paracetamol (PR) and sulfadiazine (SD) using a carbon paste electrode modified with a newly synthesized sulfathiazole–barbituric acid azo dye (SBAD). The SBAD compound was synthesized through a diazotization–coupling reaction and its molecular structure was successfully characterized by spectroscopic techniques. The electrochemical behaviour of the fabricated SBAD- modified carbon paste electrode (SBAD/MCPE) was systematically investigated and demonstrated excellent electrocatalytic activity toward the concurrent detection of PR and SD. The developed sensor exhibited good analytical performance with low limits of detection of 7.9 µM for PR and 4.11 µM for SD, along with satisfactory repeatability, reproducibility, and long-term stability. Furthermore, important experimental parameters including pH, scan rate, and interference effects were carefully optimized to achieve enhanced sensing performance. The proposed sensor offers a simple, sensitive, and cost-effective platform for the simultaneous electrochemical analysis of pharmaceutical and biological analytes.