Metal-catalyzed hydrosilylation of alkynes is an ideal atom-economic method to prepare vinylsilanes that are useful reagents in the organic synthesis and silicone industry. Although great success has been made in the preparation of β-vinylsilanes by metal-catalyzed hydrosilylation reactions of alkynes, reported metal-catalyzed reactions for the synthesis of α-vinylsilanes suffer from narrow substrate scope and/or poor selectivity. Herein, we present selective Markovnikov hydrosilylation reactions of terminal alkynes with tertiary silanes using a dicobalt carbonyl N-heterocyclic carbene (NHC) complex [(IPr) 2 Co 2 (CO) 6 ] (IPr = 1,3-di(2,6-diisopropylphenyl)imidazol-2-ylidene) as catalyst. This cobalt catalyst effects the hydrosilylation of both alkyl-and aryl-substituted terminal alkynes with a variety of tertiary silanes with good functional group compatibility, furnishing α-vinylsilanes with high yields and high α/β selectivity. Mechanistic study revealed that the stoichiometric reactions of [(IPr) 2 Co 2 (CO) 6 ] with PhCCH and HSiEt 3 can furnish the dinuclear cobalt alkyne and mononuclear cobalt silyl complexes [(IPr)(CO) 2 Co(μ−η 2 :η 2 -HCCPh)Co(CO) 3 ], [(IPr)(CO) 2 Co(μ-η 2 :η 2 -HCCPh)Co(CO) 2 (IPr)], and [(IPr)Co(CO) 3 (SiEt 3 )], respectively. Both dicobalt bridging alkyne complexes can react with HSiEt 3 to yield α-triethylsilyl styrene and effect the catalytic Markovnikov hydrosilylation reaction. However, the mono(NHC) dicobalt complex [(IPr)(CO) 2 Co(μ-η 2 :η 2 -HCCPh)Co(CO) 3 ] exhibits higher catalytic activity over the di(NHC)-dicobalt complexes. The cobalt silyl complex [(IPr)Co(CO) 3 (SiEt 3 )] is ineffective in catalyzing the hydrosilylation reaction. Deuterium labeling experiments with PhCCD and DSiEt 3 indicates the synaddition nature of the hydrosilylation reaction. The absence of deuterium scrambling in the hydrosilylation products formed from the catalytic reaction of PhCCH with a mixture of DSiEt 3 and HSi(OEt) 3 hints that mononuclear cobalt species are less likely the in-cycle species. These observations, in addition to the evident of nonsymmetric Co 2 C 2 -butterfly core in the structure of [(IPr)(CO) 2 Co(μ-η 2 :η 2 -HCCPh)Co(CO) 3 ], point out that mono(IPr)-dicobalt species are the genuine catalysts for the cobaltcatalyzed hydrosilylation reaction and that the high α selectivity of the catalytic system originates from the joint play of the dicobalt carbonyl species to coordinate alkynes in the Co(μ-η 2 :η 2 -HCCR′)Co mode and the steric demanding nature of IPr ligand.