Instrumented Charpy impact testing has been used for evaluating the dynamic fracture behaviour of mis-matched Q & T steel weldments. The effect of strength mis-match on the dynamic fracture toughness (JId) and dynamic crack resistance curves (Jd-R) of HAZ and weld metals specimens are discussed. The crack propagation and mode of failure due to impact loading are analyzed through SEM and correlated with dynamic resistance curves. © Elsevier Science Ltd.