A debris trap is mounted within a bottom nozzle of a fuel assembly so as to capture and retain debris carried by coolant flowing from the lower core plate openings of the nuclear reactor to the fuel assembly. The trap includes a hollow enclosure disposed below the adapter plate of the bottom nozzle and between the corner legs of the nozzle. The enclosure is composed of upper and lower walls and a continuous side wall which spaces apart the upper and lower walls and interconnects their peripheries so as to form a debris capturing and retaining chamber within the hollow enclosure. The walls are composed of a material, such as wire mesh screen, which is permeable to liquid coolant but impermeable to debris. A plurality of wall sections severed from the lower wall and bent into the chamber of the enclosure define a plurality of openings into the chamber. The openings and wall sections which define them are oriented relative to the direction of coolant flow through the enclosure such that any debris which enters the chamber through the openings will be substantially detered from exiting back through the openings. Also, leaf springs are attached to opposite sides of the enclosure and engagable with a pair of corner legs of the bottom nozzle for releasably locking the trap enclosure in place in the bottom nozzle. Further, a central annular sleeve mounted between the upper and lower walls of th enclosure bolsters the structural integrity of the debris trap.