Fusion bonding is an attractive technology for joining polymer matrix composites. The advantages of using this technique are good environmental resistance, high strength (ideally that of the parent materials), and the lack of any mechanical fasteners. This study presents a model for predicting the through transmission ultrasonic (TTU) amplitude response of multilayered composite media having a thermal gradient through the thickness, as seen in a fusion bonding process. The received TTU amplitude is predicted as a function of temperature at the interface of interest. The model response to frequency and layer stacking sequence was investigated.