Purpose: The aim of this study was to evaluate dentin sealing ability and microshear bond strength of two different resin cements. Materials and Methods: Resin composite overlays (Estenia C&B) were fabricated and cemented to mid-dentin surfaces with either a self-adhesive resin cement (RelyX Unicem) or a resin cement with a self-etching primer (Panavia F2.0). After 24 h storage in water, the specimens were sectioned, placed into 50% (w/v) ammoniacal silver nitrate solution for 24 h, exposed to photodeveloping solution and observed using FE-SEM and EDS. Percentage distribution of metallic silver particles in the resin cement/dentin interface was calculated using digital image analysis software. In addition, small resin overlay cylinders were also bonded to dentin using either of the resin cements, and their bonding performance was evaluated with the microshear bond strength test. The statistical significance was defined as p = 0.05. Results: No statistically significant difference was detected in the microshear bond strength between RelyX Unicem and Panavia F2.0 (24.9 ± 4.8 and 26.1 ± 5.3 MPa, respectively, p > 0.05). However, a significant difference was detected in silver particle penetration percentage between RelyX Unicem and Panavia F2.0 (7.4 ± 4.6 and 18.7 ± 8.7 MPa, respectively). The Kruskal-Wallis mean ranks for nanoleakage were 6.8 and 14.2, respectively (p 0.05). Conclusion: While the bond strengths of the two materials were comparable, the self-adhesive resin cement may provide better dentin sealing compared to the self-etching primer resin cement. Keywords: nanoleakage, microshear bond strength, resin cement, self-adhesive, self-etching primer