Objectives: To evaluate the histopathological changes in mechanically exposed dog pulps capped with three self-etching adhesive systems. Material and Methods: Seventy-two Class V cavities were prepared under rubber dam isolation in dogs. The pulps were exposed and capped with Clearfil SE Bond (Kuraray), Imperva FluoroBond (Shofu), Prompt L-Pop (3M ESPE), and Dycal (Dentsply; control capping agent), respectively. Histopathological examination of the teeth was performed at 7, 14, and 30 days post-operatively. Hematoxylin-eosin staining was performed to assess the inflammatory cell response, tissue disorganization, and hard tissue formation. Brown & Brenn staining was used to detect the presence of bacteria. The data were analyzed by Kruskal-Wallis and Nemenyi tests. Results: Most pulps showed moderate to severe inflammatory response. Hard tissue formation appeared at 14 to 30 days. Positive bacterial staining was observed in most specimens in experimental groups. The histological changes in the pulps of the experimental groups were more pronounced than in the control group. Differences in inflammatory response, tissue disorganization, and hard tissue formation were observed among teeth treated with the three self-etching systems. Conclusion: Microleakage has a critical influence on pulpal repair. It is not beneficial to cap the pulp with self-etching adhesive systems. Diverse pulpal responses were observed to the self-etching adhesive systems, and the histological changes were more pronounced than in the control pulps treated with Dycal. The effects of the self-etching adhesive systems are such that these materials require further study to address issues of bacterial microleakage during placement of restorations. Keywords: adhesive system, direct pulp capping, self-etching