Research excavations were carried out between 2017-2018 in order to restore the Istanbul Gate of Iznik (Nicaea) and its surrounding walls. In this study, 23 complete and almost complete clay lamps obtained from the excavations were investigated. One of these 23 clay lamps is a Pontic production, two of them are North African productions and one is an Asia Minor production. Also, the origin of production of 19 clay lamps was identified and classified as "Iznik Local Production". These lamps, probably produced between the 5th and 7th centuries, were compared to the results of the Roman Theatre Excavation and the properties of Anatolian lamp productions such as shape and decoration for identification and classification. Moreover, a "leaf / ivy leaf" motif is identified at the bottom of the two lamps, which was most probably used as a workshop mark in Nicaea. Supportively, the leaf pattern is also associated with both the Dionysus cult and the fertile soil of Nicaea where pottery had been produced for centuries.