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 structure disposed below the adapter plate of the bottom nozzle and between the corner legs of the nozzle. The structure is composed of a plurality of straps aligned with one another in a crisscross arrangement and defining a plurality of interconnected wall portions which form a multiplicity of small cells each having open opposite ends and a central channel for coolant flow through the trap. A plurality of spring-like fingers are punched out of the wall portions and bent to extend into the cell channels toward the downstream end of the trap structure to provide means to capture and retain pieces of debris carried through the channels by flowing coolant. Outwardly projecting tabs are provided on the upstream end of the trap structure for holding large pieces of debris to prevent lateral circulation thereof along, and repeated impact thereof against the structure. Also, leaf springs are attached to opposite sides of the structure and engagable with a pair of the corner legs of the bottom nozzle for releasably locking the trap structure in place in the bottom nozzle.