Introduction: The purpose of this study was to assess the effect of blood and saliva contamination on the shear bond strength of 4 orthodontic adhesives. Methods: Four adhesives (Transbond XT primer [3M Unitek], Monrovia, Califl, Transbond Plus self-etch primer [3M Unitek], Assure hydrophilic primer [Reliance, Itasca, III], and SmartBond cyanoacrylate [Gestenco, Gothenburg, Sweden]) were used to bond stainless steel maxillary central incisor brackets to 120 bovine permanent mandibular incisors. The teeth were randomly divided into 12 groups of 10 specimens, and each primer-adhesive combination was tested under different enamel conditions: dry, and blood and saliva contamination after priming. Shear forces were applied to the samples with a testing machine. Bond strengths were measured in megapascals. Results: Statistical evaluations showed that the shear bond strength of the SmartBond cyanoacrylate adhesive group was significantly lower than all other groups; however, it was the only adhesive that was not affected by contamination. Saliva and blood contamination resulted in significant drops in shear bond strengths of the Transbond XT and Assure groups. Transbond Plus self-etch primer was also negatively affected by blood contamination, although it was suitable for bonding with saliva contamination.