The invention is directed to a process for the laser welding of two filter half-trays made of plastic and used in automatic transmission oil filters, wherein two filter half-trays are placed one on top of the other and welded along their common edge using laser light, one filter half-tray consisting of laser light-permeable plastic and the other filter half-tray of laser light-impermeable plastic, and the laser beam is passed through the laser light-permeable filter half-tray along the position of contact with the other filter half-tray, striking the laser light-impermeable filter half-tray, and co-fusing of the two filter half-trays within the welding zone is achieved by light absorption of the laser light-impermeable plastic material.