The present disclosure relates to a separator for a secondary battery including a dual porous coating layer of inorganic particles with different surface characteristics, a secondary battery including the same, and a method of manufacturing the separator. According to an exemplary embodiment of the present disclosure, a separator including a porous substrate, a first porous coating layer, and a second porous coating layer is provided. According to the present disclosure, a method of manufacturing a separator including forming a first slurry, forming a second slurry, forming a first porous coating layer, and forming a second porous coating layer is provided. A separator according to the present disclosure has uniform dispersion of inorganic particles in a coating layer of the separator, and adsorbs an excess of metal ions generated in the battery when the battery is out of a normal operating temperature range, thereby ensuring safety of the battery.