Provided are reinforcing fibers using an adhesive component not containing resorcinol and formaldehyde, which are excellent in adhesiveness to rubber and which can be efficiently produced while preventing contamination of production facilities, and a method for producing them, as well as a molded article using them. The reinforcing fibers have an adhesive component that contains a conjugated diene rubber and an oil, in at least a part of the surfaces thereof, wherein the vapor pressure at 20° C. of the oil is 10 Pa or less.