Biocidal branched quaternary ammonium polymers are made by condensing a difunctional halide with a trifunctional tertiary amine and optionally with a difunctional amine. The branched quaternary ammonium polymers have 2-dimensional conformation that provides better coverage over the surfaces of microorganisms and enhances efficacy as biocides as compared to most commercially available linear (one-dimensional) quaternary ammonium polymers. The bulkier 2-dimensional conformation of this invention limits the uptake, accumulation and release of these branched polymers to and from contact lenses. Therefore, these branched quaternary ammonium polymers can reduce the cytotoxicity, enhance compatibility and suitable for ophthalmic use. The highly branched polymers can be prepared with minimum or no difunctional tertiary amines. The lightly branched polymers can be prepared with of a minimum ratio of trifunctional tertiary amines/difunctional tertiary amines.