Objective: The purpose of this study was to compare the effects of experimentally derived surfactant-containing acid gel with those of different surface-conditioning agents on microleakage of unfilled and filled sealants applied to permanent teeth following noninvasive and invasive procedures. Method and materials: Four main groups of surface-conditioning agents (NRC; NRC + Prime&Bond NT; Email Preparator Blue; and experimental acid gel) were subdivided into 16 subgroups (n = 8). Subgroups were designed according to the surface preparation procedures applied (noninvasive and invasive) and fissure sealants used (Helioseal and Helioseal F). After application of the test materials, the specimens were subjected to thermocycling and then immersed in 0.5% basic fuchsin dye. Following sectioning, specimens were examined under a stereomicroscope and microleakage scores were assigned. Results: Subgroups 9 (Email Preparator Blue + Helioseal), 11 (invasive + Email Preparator Blue + Helioseal), 13 (experimental acid gel + Helioseal), and 15 (invasive + experimental acid gel + Helioseal) showed no microleakage. The differences between those subgroups and subgroups 1 (NRC + Helioseal), 2 (NRC + Helioseal F), 3 (invasive + NRC + Helioseal), 4 (invasive + NRC + Helioseal F), 5 (NRC + Prime&Bond NT + Helioseal), and 6 (NRC + Prime&Bond NT + Helioseal F) were statistically significant. Conclusion: Email Preparator Blue and surfactant-containing experimental acid gel, combined with an invasive/noninvasive surface preparation procedure and Helioseal, significantly prevented microleakage.