Abstract: The multifunctional characteristics of barium zinc vanadate (BaZnV₂O₇) nanoparticles (BZV NPs) were explored in this study, focusing on their photocatalytic activity, supercapacitor performance, and sensing abilities. X-ray diffraction analysis confirmed that the crystallites were 40.3 nm in size, whereas ultraviolet visible diffuse reflectance spectroscopy revealed an energy bandgap of 5.28 eV. Functional groups, elemental composition, and morphology were assessed using Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and scanning electron microscopy, respectively. The photocatalytic efficiency of the BZV NPs was evaluated at various catalyst dosages, dye concentrations, and pH levels, for the degradation of acid black-52 (AB-52) dye under UV light. Cyclic voltammetry and galvanostatic charge-discharge analyses were performed to determine the energy storage and cyclic stability of the BZV-NP-modified carbon paste electrode. In addition, a novel electrochemical sensor based on BZV was developed to accurately detect the concentration of biomolecules and chemical drugs. BZV nanoparticles exhibited remarkable photocatalytic dye degradation up to 80.4%, indicating their application in waste water treatment. The BZV-NP-modified carbon paste electrode exhibited a superior specific capacitance of 720 F·g⁻¹ with excellent cycling stability over 1000 cycles. The electrodes efficiently detected biomolecules such as ascorbic acid and uric acid, chemical drugs including paracetamol and ibuprofen, and heavy metals such as mercury, cobalt, and cadmium in the concentration range of 1–5 mM. The limit of detection (LOD) was measured for all analytes, and the electrode exhibited high sensitivity. These multifunctional properties render BZV promising material for energy storage and environmental monitoring applications.