Bilirubin oxidase (BOD) from Bacillus pumilus shows high thermostability in solution and high reactivity at high temperature for ABTS oxidation. When BOD is incorporated into a cross-linked redox-active hydrogel film consisting of pendant osmium moieties grafted on a polyvinylimidazole backbone on GC electrode, high catalytic current per enzyme molecule was achieved with redox mediator in a broad pH range from 4 to 7. The maximum current was increased with increasing the electrolyte temperature as high as 70 °C.