New phosphate based on manganese, chromium, and sodium, with alluaudite-like structure, namely Na2Mn2Cr(PO4)(3), was synthesized by solid-state reaction and characterized by X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. The magnetic properties were evaluated as well. The Rietveld method was applied to refine the structure of the obtained compound. The prepared powder was used as a modifier of carbon paste electrode to investigate the sensing of lead ions in aqueous solution by means of square wave voltammetry. The impact of electrochemical and chemical parameters on the current intensity was optimized. Under optimized conditions, the prepared electrode had a detection limit of 0.25 mu M. Due to its good detection performance, the proposed sensor was applied to determine lead ions in real wastewater matrices.