Objectives: The purpose of this study was to evaluate the marginal leakage in Class V composite resin restorations of deciduous teeth after air abrasion and conditioning agents. Methods: The preparations were made on the facial and lingual tooth surfaces of 25 molars, using burs in high speed handpiece. The teeth were divided in 5 groups: G1 (air abrasion and Scotchbond Multi Purpose), G2 (phosphoric acid and Scotchbond MP), G3 (Clearfil SE Bond), G4 (air abrasion, phosphoric acid and Scotchbond MP) and G5 (air abrasion, Clearfil SE Bond); all groups were restored with Z100 composite resin. After polish, the teeth were subjected to 500 thermal cycling and immerged in 50% silver nitrate solution. After sectioning, the specimens were analyzed with a stereomicroscope (40x) for assessment of microleakage according to the degree of dye penetration (scores of 0-4). Data were analyzed by Kruskal-Wallis one-way ANOVA and Mann-Whitney tests. Results: Groups 1 and 2 showed greater leakage on the gingival margin. In group 3, greater leakage was observed on the occlusal margin and groups 4 and 5 demonstrated no statistical differences in marginal leakage between gingival and occlusal margins. Group 1 presented the greatest leakage scores on gingival and occlusal margins. Groups 3, 5, 2 and 4 presented decresing leakage on the occlusal margin. No statistical difference was found between groups 4 and 2, as well as between the groups 3 and 5. Conclusion: It was concluded that the association of air abrasion with conditioning acids is not required in order to decrease the microleakage in composite restorations of deciduous teeth.