Abstract Hydrogen emission by wood‐feeding termites, Coptotermes formosanus, Reticulitermes flavipes and Reticulitermes virginicus, was investigated upon a cellulosic substrate as their food source. The emission rates among the three species tested were significantly different and R. virginicus demonstrated the greatest H2 emission at 4.78 ± 0.15 μmol/h/g body weight. In a sealed test apparatus, H2 emission for each termite species showed a quick increase at the initial incubation hours (3–6 h), followed by a slower growth, possibly due to the feedback inhibition by gas accumulation. Further investigation revealed that continuous H2 emission could be maintained by reducing the H2 partial pressure in the sealed container. The bioconversion of cellulose to molecular H2 by the subterranean termites tested could reach as high as 3 858 ± 294 μmol/g cellulose, suggesting that the termite gut system is unique and efficient in H2 conversion from cellulosic substrate.