A separator for a rechargeable battery, a method of preparing a separator, and a rechargeable lithium battery, the separator including a porous substrate; and at least one coating layer on one surface of the porous substrate, wherein the coating layer includes a fluorine-containing binder, a filler, and an additive, the fluorine-containing binder has a concentration gradient in which a concentration thereof in the coating layer increases toward an outer surface of the separator in a thickness direction of the separator, an infrared spectral intensity of a C—F group of the fluorine-containing binder is greater than 0.0030 to less than 0.0050, the additive is a hydrocarbon polymer compound that includes a carboxyl group, and a weight average molecular weight of the hydrocarbon polymer compound is about 5,000 g/mol to about 15,000 g/mol.