Summary: This study reports the development of an SWCNT-modified polyaniline electrochemical sensor for the simultaneous detection of levodopa (LD) and benserazide (BS), essential drugs in Parkinson’s disease treatment. The sensor, fabricated through electropolymerization of aniline on a glassy carbon electrode (GCE) and modified with SWCNTs, exhibited enhanced electron transfer kinetics, increased surface area, and improved sensitivity. Under optimized conditions (pH 7.0, 1.0% SWCNT solution), the sensor demonstrated linear detection ranges of 500–1000 µM for LD and 100–500 µM for BS, with detection limits of 183.2 µM and 44.5 µM, respectively. Notably, ascorbic acid interference was minimized, ensuring selectivity. Validation studies using pharmaceutical tablets and human urine samples confirmed high accuracy and reliability. The rapid response, cost-effectiveness, and potential for miniaturization make this sensor a valuable alternative for real-time pharmaceutical and clinical monitoring of LD and BS.