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Abstract Copper acetylides are readily available and especially convenient reagents for the alkynylation of a broad range of heteronucleophiles. Upon simple activation with molecular oxygen in the presence of suitable ligands and solvents, they readily transfer their alkyne moiety at room temperature, notably yielding a variety of nitrogen- and phosphorus-substituted alkynes. We report in this manuscript an extensive study of the chemoselectivity of this alkynylation based on quantitative 13C NMR analyses. With suitable ligand/solvent combinations, various phosphorus-based nucleophiles can be alkynylated with excellent levels of selectivity, even in the presence of a large excess of a nitrogen-nucleophile. This chemoselective alkynylation could be further extended to an even more challenging selective alkynylation of a nitrogen-nucleophile over another one, further highlighting the synthetic potential of copper acetylides as alkynylating agents that can selectively "fish" a nucleophile without affecting others. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]