The aim of this study was to compare the shear bond strengths (SBS), failure modes (adhesive, cohesive, or mixed), and marginal microleakage occurrence of conventional resin (CR)-based, glass ionomer (GI)-based, and self-adhesive resin (SAR)-based fissure sealants with or without prior phosphoric acid (PA) etching. Fifty extracted premolars were randomly and equally assigned into five groups -G1:PA+CR, G2:PA+GI, G3:GI, G4:PA+SAR, and G5:SAR. Prior PA etching significantly (p<0.05) increased the SBSs of sealants. Adhesive failure mainly occurred in teeth treated with SAR- or GI-based fissure sealants, and cohesive failure mainly occurred in PA-etched teeth. Microleakage occurrence differed significantly (p<0.05) among the five groups of treated teeth. We concluded that conditioning of a tooth's enamel surface is crucial to creating strong bonds and leak-free sealing between tooth and fissure sealant.