Transition metal-mediated copolymerizations of diazocarbonyl compounds with alkynes and an isocyanide were investigated with the following combinations of the comonomers: (E)-1-diazo-3-nonen-2-one (1a) with phenylacetylene (2a), (E)-1-diazo-4-phenyl-3-buten-2-one (1b) with 1-heptyne (2b), ethyl diazoacetate (1c) with 2a and 2b, and 1b with tert-butyl isocyanide (3). All the copolymerizations afforded random copolymers whose GPC traces were unimodal, and H-1 NMR spectra exhibited superposition of signals derived from the repeating units of both comonomers. In addition, the progress of the copolymerizations was supported by the DSC analyses of the products.