Scallops are an important cultured bivalve species in China. Prior to artificial reproduction, it is essential to segregate male and female parent scallops and monitor gonadal development to determine the optimal timing for seedling production. Currently, scallop gender and gonad maturity were assessed in vivo by stimulating the soft tissues with foreign body or by drying in the shade to induce shell opening, followed by visual inspection of gonad color. These traditional methods were time-consuming and conducted out of water, which can lead to stress-induced mortality of parent scallops and compromised control over seedling production. In this study, we employed a novel endoscopic approach to identify scallop gender and gonadal maturity. This method relies on the coloration of gonads captured in images obtained via a probe inserted through the byssus orifice between the shells. Our results demonstrated that scallop gonad color and gender could be clearly visualized using the endoscope without direct contact with the delicate soft tissues, even when the scallops remained in a closed state. The time required for this method was approximately half that of traditional foreign body stimulation and one-quarter that of dry-in-shade method. Moreover, the endoscope could capture clear images of scallop gonads in seawater, enabling in situ observation. This non-invasive endoscopic technique eliminates the need to induce shell opening, allowing for accurate and rapid gonad observation and gender identification, thereby enhancing the efficiency of scallop breeding.