Statement of problem: Polymerization shrinkage stress is the most important causal factor in the microleakage of composite restorations. Relief of this stress with application of low intensity light and low elasticity liner may lead to a decrease in microleakage.Purpose: The aim of this study was to evaluate the effect of light intensity and flowable composite on the microleakage of class V microhybrid composite restorations.Materials and method: In this experimental study, 56 intact bovine incisior teeth were selected. Standard class V cavities were prepared in buccal surfaces and the teeth were randomly divided into 4 groups of 14. All teeth were restored with Tetric ceram and Excite was used as bonding system: Group 1: conventional cure with 40 seconds 550 mW/cm2 light intensity. Group 2: soft- start (s.s) cure with initial intensity (10 seconds 150 mW/cm2) and then final intensity (30 seconds 550 mW/cm2). In groups 3 and 4: the same curing methods were as groups 1 and 2 perfomed, but flowable composite (Tetric flow) was used as liner. After 24 hours water storage samples were, thermocycled, and were immersed in 2% methylene blue for 24 hours. Dye penetration was evaluated using stereomicroscope. The statistic analyses were performed by Kruskal-Wallis and Mann-Whitney testsResults: In general, the gingival margins had significantly more microleakage than the incisal margins (p<0.05). Microleakage at gingival margin significantly increased with application of flowable liner and soft-start curing (p<0.05).Conclusion: The result of this study indicated that soft start curing and flowable liner significantly increase microleakage at the gingival margin.Key words: Microleakage, Soft- start curing, Conventional curing, Flowbale liner, Light intensity