Objectives: The purpose of this study was to characterize the interfacial ultra-structure of a self-adhesive composite resin Exp.564 (experimental, 3M ESPE, Seefeld, Germany) at enamel and dentin using transmission electron microscopy (TEM). Methods: Non-carious human third molars were used within one month after extraction. The experimental self-adhesive composite resin was built up to bur-cut (medium-grit: 100 µm) enamel, and to fractured (smear free) and bur-cut dentin, and light cured 20-sec, strictly according to the manufacturer's instructions. After building up procedures, specimens were stored for 1 day in distilled water at 37°C. Subsequently, non-demineralized/demineralized 70-90 nm sections were prepared following common TEM-specimen processing procedures, including fixation, gradual dehydration, embedding, and diamond-knife ultra-microtomy. Results: The experimental self-adhesive composite resin showed a typical micro-hybrid filler distribution. At bur-cut enamel, a tight interface was formed, mostly with only tiny micro-tags and without distinct dissolution observable. At fractured dentin, a relatively thin hybrid layer of maximum a few hundreds of nanometer was formed without clear surface demineralization. Distinct resin tags were formed due to the absence of smear plugs. At bur-cut dentin, the interaction of the experimental self-adhesive composite resin appeared superficial, with the surface structure being more irregular in case of bur preparation. No clear resin tags were formed due to the obstruction of dentin tubules with smear plugs. Silver-nitrate infiltration showed a pattern of spot-like appearance of nano-leakage. Ag-infiltration was observed along the dentin-adhesive interface of bur-cut dentin, as compared to that of fractured dentin. Conclusion: The obtained tight interface at both enamel and dentin demonstrates the self-adhesive capacity of the experimental self-adhesive composite resin.