The purpose of this study was to compare the shear bond strength of different adhesive systems for bonding orthodontic brackets under non-contaminated and artificial saliva-contaminated conditions. One hundred and sixty maxillary first premolars were divided into eight groups of twenty. Stainless steel brackets were bonded using one of the following adhesive systems: conventional adhesive system (TransbondTM XT), or moisture-resistant adhesive systems (TransbondTM Plus Color Change, Beauty Ortho Bond® and Assure®) on both non-contaminated and artificial saliva-contaminated enamel. Shear bond strength was measured using an Instron® Universal Testing Machine. Analysis of variance and Tukey’s test were used to compare the differences in the mean values. The results show that the mean shear bond strength of TransbondTM XT under noncontaminated conditions (11.70±3.14 MPa) was significantly superior to that of the other systems, both under non-contaminated and artificial saliva-contaminated conditions (p < .05), whereas the mean shear bond strength of TransbondTM XT under artificial salivacontaminated conditions (7.24±1.86 MPa), TransbondTM Plus Color Change under noncontaminated and artificial saliva-contaminated conditions (7.37±1.59 and 6.44±1.40 MPa, respectively), Beauty Ortho Bond® under non-contaminated and artificial salivacontaminated conditions (6.28±2.05 and 6.66±2.01 MPa, respectively), and Assure® under non-contaminated and artificial saliva-contaminated conditions (6.74±1.61 and 7.28±1.06 MPa, respectively) were not significantly different. In conclusion, artificial saliva contamination significantly decreased the mean shear bond strength of TransbondTM XT, but did not affect the mean shear bond strength of the other systems. Nevertheless, the mean shear bond strength of all systems was greater than 6 MPa, which is clinically acceptable for bonding orthodontic brackets.