Biodentine is a tricalcium silicate cement used as a dentin replacement in restorative dentistry. The aim of this study was to assess the influence of cavity moisture on the immediate sealing and morphology of the interface between Biodentine and the dental tissues. 20 class II cavities were prepared in extracted teeth. 10 cavities were dried using the air spray before restoring with Biodentine and 10 cavities were preserved moist for the restorative procedure. The teeth were subjected to a microleakage test and then the axial sections were observed under optical microscope and scanning electron microscope. In most situations Biodentine provided an immediate good marginal sealing and a tide contact with adjacent tissues in both occlusal and cervical margins which did not seem to be influenced by the moisture of the dental supporting tissues.