A highly selective and sensitive monohydrogen phosphate (MHP) sensor has been fabricated by constructing a poly vinyl chloride (PVC) matrix membrane containing a new oxo-molybdenum methyl-salen (MS) as a neutral carrier, hexadecyltrimethyl ammonium bromide (HTAB) as a cationic additive, benzylacetate (BA) as a plasticizing solvent mediator. The membrane sensor exhibits linear potential response in the concentration range of 1.0 ×10-1 - 4.0 × 10-7 mol L-1 of MHP. The electrode displays a Nernstian slope of -28.6 ± 0.3 mV decade-1 in the pH of 8.5. The proposed sensor also exhibits a fast response time of