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Self-etching primer adhesives have recently been introduced to simplify bonding. However, the fundamental bonding mechanism of self-etching primers to enamel is not yet fully understood. This study aimed to investigate resin–enamel bonds of self-etching primer adhesives on ground enamel. Two self-etching primer adhesives (Clearfil Liner Bond 2 V and Clearfil SE Bond) were used in this study. A total-etch adhesive (One-Step) was used as a control. Resin–enamel beams were subjected to the microtensile bond test. Subsequently, the failure modes of all specimens were quantified using image analysis. Undemineralized and demineralized ultrathin sections of the resin–enamel bonded specimens were examined using transmission electron microscopy. The bond strengths of Clearfil SE Bond (39.8 ± 11.9 MPa) and One-Step (46.2 ± 12.7 MPa) were significantly greater than that of Clearfil Liner Bond 2V (30.4 ± 6.2 MPa). Scanning electron microscopy of the fractured surfaces revealed the failure direction and weakest portion within each bond. Transmission electron microscopy showed a thin hybridized complex of resin in enamel produced by the self-etching primers without the usual micrometer-sized resin tags seen in resin–enamel bonds produced using the total-etch adhesive. The morphological features of the resin–enamel bonds produced by two self-etching primers tested were different from that created with the total-etch adhesive. [ABSTRACT FROM AUTHOR]