2H-Azirine-2-carbonyl azides undergo a rearrangement into derivatives of 2-(1H-tetrazol-1-yl)acetic acid when interacting with O- and S-nucleophiles at room temperature. The reaction is catalyzed by tertiary amines or hydrazoic acid. The reaction with primary alcohols and phenols gives alkyl/aryl 2-(1H-tetrazol-1-yl)acetates. Thiophenols react with 2H-azirine-2-carbonyl azides to afford S-aryl 2-(1H-tetrazol-1-yl)ethanethioates. The mechanism of the nucleophile-induced rearrangement of 2H-azirine-2-carbonyl azides is discussed on the basis of DFT calculations as well as kinetic and 15N labeling experiments.