A novel organosilane compound having polymerizability is disclosed which is a vinyl .omega.-triorganosilyl n-undecanoate of the formula CH.sub.2 .dbd.CH--O--CO--(--CH.sub.2 --).sub.10 --SiR.sub.3, in which R is an alkyl group having 1 to 4 carbon atoms, alkoxy group having 1 to 4 carbon atoms or trialkyl siloxy group of which the alkyl group has 1 to 4 carbon atoms. This compound can be prepared by the hydrosilylation reaction between a triorganosilane of the formula HSiR.sub.3 and vinyl 10-undecenoate of the formulaCH.sub.2 .dbd.CH--O--CO--(--CH.sub.2 --).sub.8 --CH.dbd.CH.sub.2in the presence of a platinum catalyst. The compound is polymerizable to give not only a homopolymer of the compound alone but also a copolymer with other comonomers such as vinyl chloride, chloro trifluoroethylene, methyl methacrylate and the like.