Purpose: To evaluate shear bond strength and microleakage of a new self-etching/self-adhesive fissure sealant on prismless enamel compared with conventional fissure sealing. Materials and Methods: A total of 90 extracted third molars were assigned to 3 main groups: group 1: selfetching/ self-adhesive sealant, without acid etching; group 2: self-etching/self-adhesive sealant, with prior acid etching; group 3: conventional fissure sealing (control group). After specimen preparation, each group was divided into 3 subgroups according to storage time (1-day water storage, 3-month water storage, and 1-day water storage followed by 5000x thermocycling). The shear bond strength was determined with a universal testing machine, according to ISO standard 29022. Afterwards, the failure mode was analyzed. An additional 24 third molars were used for microleakage assessment. The fissure pattern was sealed in strict accordance with the manufacturers' instructions. After thermocycling, the dye penetration was examined. Data were analyzed using the Mann-Whitney U-Test at a significance level of 0.05. Results: The shear bond strength of the self-etching/self-adhesive fissure sealant without prior acid etching was significantly lower (4.3 MPa) than that of the self-etching/self-adhesive fissure sealant with prior acid etching (17.1 MPa) and the conventional fissure sealing (19.1 MPa). Microleakage was significantly lower in the control group (1.1%) and in the group with the self-etching/self-adhesive sealant with prior acid etching (0.8%) compared to the group that used the self-etching/self-adhesive material alone (49.4%). Conclusion: The self-etching/self-adhesive fissure sealant can be recommended for clinical use when enamel is etched with phosphoric acid. The self-etching/self-adhesive sealant without prior acid etching showed significantly inferior results. Palabras clave: pit-and-fissure sealant, shear bond strength, microleakage, self-etching sealant, self-adhesive sealant