As a natural product, chitosan has the inherent properties of being biodegradable, biocompatible and nontoxic. These properties render it an ideal matrix in enzyme immobilization for clinical analysis. In this work, the feasibility of electrochemical biosensor fabrication using chitosan has been demonstrated. As a test case, the enzyme, sulfite oxidase (SOD), was covalently immobilized onto the matrix of chitosan‐poly(hydroxyethyl methacrylate) (chitosan‐HEMA), a natural/synthetic polymer hybrid material obtainable via a UV curing process. An electron transfer mediator, p‐benzoquinone was coupled onto the polymer network for the activation of chitosan‐HEMA copolymer after the photo‐induced polymerization reaction. The biological activity of the immobilized SOD and the electroactivity of the coupled p‐benzoquinone were examined.