N-Nitroso-3-morpholinosydnonimine 3 was prepared by nitrosation of SIN-1 and characterized by 1H-NMR, 13C-NMR, and HRMS. Its structure, confirmed by single crystal X-ray diffraction analysis, was found to be in agreement with its mesoionic and aromatic character. Unlike 3-morpholino-sydnonimine (SIN-1), which releases both nitric oxide and superoxide radical, decomposition of this nitrosylated sydonimine could yield nitric oxide as the only decomposition product, and thus without the formation of toxic peroxynitrite.