INTRODUCTION: Composite restorative materials represent one of the many successes of modern biomaterials research, since they replace biological tissue in both appearance and function. Several aspects during selection of composite restorative materials should be considered, among which are the degree of conversion and microleakage. OBJECTIVES: The objective of this study is to compare the degree of conversion and microleakage in bulkfill flowable and conventional flowable composite. MATERIALS AND METHODS: Bulk-fill flowable composites (SDR, Dentsply), (Filtek Bulkfill flowable, 3M ESPE) and conventional flowable composite (X-Flow, Dentsply), (Filtekz350xt flowable, 3M ESPE) were tested. 28 cylindrical specimens were prepared from each material in Teflon mold. Degree of conversion (DC) was determined using Fourier transform infrared spectroscopy (FTIR) test. 44 non-carious molars were selected and Class V cavities were made and filled with composite in bulk increment then immersed in a basic fuschine dye. Samples were sectioned in the center of the restoration and observed with a 40x stereomicroscope; extent of dye penetration was measured. Statistical analysis of the results was performed using ANOVA and Post Hoc for DC, Kruskall-Wallis and Mann Whitney test for microleakage. RESULTS: A statistically significant difference was recorded for the degree of conversion test between the groups with p (<0.001). Microleakage test showed no statistically significant difference between the four groups at occlusal margins with p=0.563, nor at the cervical margins with p=0.243. CONCLUSIONS: Within the limitations of the current study, it was concluded that the bulkfill flowable composite (SDR) had better DC in comparison to the other three flowable composites used in the study. It was also concluded that it had the best marginal seal in both occlusal and cervical margin among all the groups.