Most denitrifiers produce the greenhouse gas nitrous oxide (N2O) due to insufficient anaerobiosis. We constructed a recombinant Pseudomonas stutzeri strain producing Fusarium oxysporum flavohemoglobin (fhb) and found that it emitted less N2O than the wild-type strain under aerobic and anaerobic conditions. The rate of N-2 production was higher than in the wild-type strain after the depletion of oxygen in culture, suggesting that fhb enhanced the reduction of N2O to N-2. The strain is the first recombinant bacterial denitrifier that reduces N2O production.