A method for waterproofing of bridges (1) and similar structures aimed at railway traffic is described, the structures comprising an arch or deck structure, on which there is placed a ballast (M) of gravel or crushed stone (2) upon which the tracks (6) extend between the two ends of the bridge (1). The waterproofing is obtained first by the removal of the tracks (6) and a reduced layer (S) of gravel or crushed stone (2), leaving in place the remaining part of gravel or crushed stone (2), and then by laying one or more sheets (10) of cured rubber on the remaining part of gravel or crushed stone (2). The thickness of the rubber is such as to be sufficiently resistant to perforation by the gravel or crushed stone (2), which is subsequently placed thereon to complete the ballast, Finally, the previously removed tracks (6) are set in place again. According to the method, a joint is made between the sheets (10) by means of a connection of mechanical type, with a positive locking shape fit, or a chemical bond using a suitable adhesive.