This study evaluated dentin surface and hybrid layer’s morphology, using copaíba (CO) emulsion as dentin biomodifier before traditional and self-etching adhesive, by environmental scanning electron microscopy (ESEM). Ninety-six third sound molars were divided into 16 groups, according to the dentin substrate, tested substances, and the adhesive system used. The conditioned dentin surface treated with clorexidina (CHX) 2% showed phosphate salts on two dentin substrates as well as the sound conditioned or not surface treated with calcium hydroxide solution (CHS), where the mineral precipitate deposition obstructs the tubules lumen. A significant difference (p <0.0001) in dentin surface morphology was observed at the CHS group on conditioned and not conditioned sound dentin. The CO emulsion produced a regular and homogenous hybrid layer with many resin tags on both dentin surfaces, irrespective of the adhesive system used, with better performance than CHS and CHX 2% (p =0.0007) on caries-affected dentin at the self-etching group. CO emulsion showed no morphological changes on sound and caries-affected dentin and presented a regular hybrid layer, regardless of the adhesive system used. Keywords: Copaiba oleoresin; Emulsions; Dentin-bonding agents; Phytotherapy.