The potential for carbon monoxide-releasing molecules (CO-RMs) as antimicrobials represents an exciting prospective in the fight against antibiotic resistance. Trypto-CORM, a tryptophan-containing manganese(I) carbonyl, is toxic against E. coli following photo-activation. Here, we demonstrate that Trypto-CORM is toxic against Neisseria gonorrhoeae in the absence of photoactivation. Trypto-CORM toxicity was reversed by the high CO affinity globin leg-haemoglobin (Leg-Hb), indicating that the toxicity is due to CO release. Release of CO from Trypto-CORM in the dark was also detected with Leg-Hb (but not myoglobin) in vitro. N. gonorrhoeae is more sensitive to CO-based toxicity than other model bacterial pathogens, and may serve as a viable candidate for antimicrobial therapy using CO-RMs.