The gelling agent for water shut-off in oil and gas wells is a composition that forms a gel to reduce or eliminate the flow of water in a gas or oil well. The composition is formed by mixing polyvinyl alcohol, a polyvinyl alcohol copolymer, or mixtures thereof with an amino-aldehyde oligomer, such as urea formaldehyde or melamine formaldehyde, with or without a cross-linker. The polymer composition can be used to minimize or completely shut off excess water production with insignificant reduction in hydrocarbon productivity.