Abstract This paper investigates the fatigue life of tubular bracing with gusset plate connections that are commonly used to connect tubular bracing in frames, whereby a gusset plate, also referred to as a knife plate in this instance, is attached to the frame and fitted into a pre-cut slot in the HSS (hollow structural section) bracing member. Owing to construction and fabrication tolerances, it may occasionally be necessary to leave an unfilled gap between the forward edge of the inserted knife plate and the end of the slot on one or both faces of the HSS. A test program was developed to investigate the effect of the gap as well as the influence of various parameters on the fatigue behaviour of knife plate connections. A common failure mode was observed on all the specimens. Fatigue stress concentration cracks that developed in the HSS walls at the forward edge of the inserted knife plate resulted in ultimate fracture of the specimen and a relatively low fatigue life.