The stability of Methyltetrazine-amine is substantially improved compared to hydrogen substituted tetrazine-amine. Superior stability of Methyltetrazine-amine allows this reagent to be used in a wider range of chemical transformations. Long-term storage of Methyltetrazine-amine, especially in aqueous buffer, is also greatly improved compared to tetrazine-amine. This reagent is supplied as an HCl salt for improved stability and easy handling.