This article focuses on the surface chemistry of an N-containing precursor, dimethylhydrazine (DMH), on Cu. DMH both adsorbs and decomposes on clean Cu at room temperature. N-N, C-N, and N-H bonds are cleaved, resulting in the immediate desorption of N-2 and CH4 and leaving DMH species that, during subsequent heating, lead to N-2 and CH4 desorption. There is evidence that CH3 groups dehydrogenate to form methylene, CH2, that inserts into Cu-C and Cu-N bonds, and leads to C2H4, C2H5N; C3H7NH2, and C3H6NH2. The activation energy of DMH decomposition on the clean surface is about 10.8 kJ/mol. The 300 K reactivity of a clean Cu surface is reduced by repeated DMH doses and temperature programmed desorption. Passivation is attributed to the alteration of active surface sites by small amounts of retained reaction products, presumably containing C, the concentration of which lie below x-ray photoelectron spectroscopy detection limits. DMH decomposition and surface synthesis pathways are discussed.