We prepared a thin film electrode consisting of a 3.3% atomic concentration of iridium nanoparticles dispersed in graphite‐like carbon (Ir‐NDC) by a simple RF sputtering method. The film structure was characterized by TEM, XPS and AFM. The TEM results showed that the Ir particles, whose average size was 2 nm, were homogenously dispersed in the carbon matrix. XPS revealed two chemical states of Ir (Ir(0) and Ir(IV)) in the film. The Ir‐NDC film electrode exhibited excellent electrocatalytic ability with regard to H₂O₂ reduction with low atomic concentration compared to the bulk Ir electrode. The effect of L‐ascorbic acid can be suppressed due to the reductive detection of hydrogen peroxide. We applied this electrode for enzymatic glutamate detection. At a detection potential of −0.15 V (vs. Ag/AgCl), we could measure the concentration of glutamate without interferences from ascorbic acid and oxygen.