Polymerization shrinkage of composites can generate stress that results in the formation of microgaps at the resin-enamel interface and marginal leakage. The aim of the present work was to evaluate the influence of surface sealants on microleakage in composite restorations. Enamel-dentin occlusal cavities were prepared in 30 non-carious upper and lower premolars. The cavities were restored with One Coat Bond SL and Brilliant New Generation (Coletene), following the manufacturers' instructions, and polished appropriately. The samples were randomly assigned to one of the following six treatment groups: Group I (Control-no sealant); Group II: Single Bond (3M/ESPE); Group III: Perma Seal (Ultradent); Group IV: Heliobond (Vivadent); Group V: Biscover LV (Bisco); Group VI: Bioforty (Biodinâmica). The samples were then immersed in 2 % aqueous methylene blue solution for 48 hours, and thermocycled 100 times from 5 ºC to 55 ºC. The obtained specimens were ground in a bucco-palatal orientation to reach the medial plane, and observed under a stereoscopic loupe at 40X. The degree of microleakage was evaluated by assessing the penetration of the dye to the tooth-restoration interface, using a 0 to 3 grading scale. The obtained data were analyzed using the Kruskal-Wallis non-parametric test. Significant differences were observed between all rebonded groups and the control group; no differences were observed among Single Bond, Perma Seal and bioforty, or between Heliobond and Biscover LV. It would seem convenient to apply a surface sealant over composite restorations to improve marginal integrity and reduce microleakage.