Complete grouting of tendon ducts is important for durability of post-tensioned prestressed concrete (PC) bridges. Voids in the ducts may induce failure of PC tendons, possibly causing a reduction in load capacity and collapse of the bridge. The wide-range ultrasonic testing (WUT) is one of the non-destructive inspection techniques. The focus of this study is to examine the applicability of the WUT to grout inspection. This paper summarizes the characteristics of the non-destructive methods available for the PC grout inspection and outlines the sensing and analyzing techniques of the WUT method performed in practice in PC bridge construction. The inspection accuracy of the WUT method was examined by comparison to a sensor-based inspection method. This paper also reports comparative investigation and discusses the advantages of the WUT method including inspection accuracy, cost performance, time efficiency and safety. It was confirmed in on-site application that the WUT method was capable of determining grout condition at a concrete cover depth of 250 mm.