Objectives: To investigate and compare heat conduction of different flowable composites. Materials and Methods: In this study, four different flowable composites; GC Gradia Direct LoFlo (GC Corporation, Tokyo, Japan), Filtek Ultimate (3M ESPE, St. Paul, USA), Grandio Flow (VOCO GmbH, Cuxhaven, Germany) and SDI Wave (SDI, Victoria, Australia) were used. Flowable composites were placed into standard molds and used according to manufacturer instructions. The samples were prepared for every brand of flowable composites. The Heat Conduction Unit's (P. A. Hilton Ltd., England) linear heat conduction module was used in determining the flowable composites heat conductivity. The data were statistically analyzed by Mann-Whitney U-test (SPSS 13.0, SPSS, Chicago, IL, USA). Results: Heat conduction values of flowable composites were found different each other. Results for GC Gradia Direct and Grandio Flow were significantly different from 3M ESPE and SDI (P < 0.05). However, result for 3M ESPE was and nonsignificant different from SDI (P > 0.005). Conclusions: Within the limits of this study, flowable composites transmit the heat. However, results for GC Gradia Direct and Grandio Flow were significantly different from 3M ESPE and SDI.