Phosphate is widely used as a nutrient in fertilizers for maximizing crop yield, which can unintentionally cause serious water contamination problems. Thus, accurate and robust phosphate sensors applicable to complex water body conditions are in great demand. In order to better understand the sensor behavior and improve the performance, we analyzed the cobalt's interaction with phosphate in aqueous solution and proposed a sensor response mechanism of Co-based nanostructured electrochemical sensors for phosphate measurements. The increased surface area obtained from the nanoscale features could contribute to the improved detection range (10 ⁻⁶ to 10 ⁻³ M) when operated in a stable measurement condition, which was identified by the proposed mechanism. It was also observed that the inclusion of nanoscale features could enhance a specific charge transfer process more prominent over the others.