Significance Denitrifying microorganisms reduce nitrate to N ₂ via nitrite, NO, and N ₂ O under hypoxic/anoxic conditions. Since these organisms are the main sources and sinks for N ₂ O in the environment, their regulatory biology controls the emission of this potent greenhouse gas. We demonstrate bet hedging in Paracoccus denitrificans when facing hypoxia: a minority of the cells synthesize NIR + NOR, the N ₂ O source, while all synthesize NOS, the N ₂ O sink, hence the population becomes a strong net sink for N ₂ O. Bet hedging is prominent below 20 °C and data indicate that it is widespread in soil organisms. This suggests a prominent role of bet hedging in controlling N ₂ O emissions that can now be tested for in other strains and in natural environments.