This study aimed to evaluate the shear bond strength (SBS) and microleakage of a new self-etch adhesive-based fissure sealant (EG) on aprismatic enamel in comparison to conventional fissure sealing with 30 s acid etching (CG). The fissures were sealed according to the manufacturer's instructions. Each group was divided into 3 subgroups: 1-day water storage, 3-month water storage, and 5,000× thermocycling. After measuring SBS using the Ultradent method, failure mode was analyzed. In additional 16 teeth, microleakage was tested using dye penetration method. Pairwise comparisons were analyzed using Mann-Whitney U-Test. Multiple linear regression was performed to assess the factors influencing on SBS. EG had significantly lower mean SBS (4.1 MPa±2.1) than the CG (17.6 MPa±6.4). CG (1.1%) performed significantly better than the EG (12.8%) in microleakage analysis. The tested EG yielded significantly inferior results and its clinical use should be decided after weighing its pros and cons.