Background: The use of removable thermoplastic appliances has become an alternative to the use of conventional fixed appliances through gradual, sequential, and consecutive dental repositioning. Aligners have become a reality. Objective: To evaluate the shear strength of orthodontic attachments made from different composites and affixed to enamel treated with two different conditioning techniques. Materials and methods: A total of 150 bovine incisors were randomly divided into 10 groups (n = 15). In groups I, III, V, VII, and IX, the tooth enamel was etched with 37% phosphoric acid, and then an adhesive was applied. In groups II, IV, VI, VIII, and X, enamel etching was performed with the self-etching agent Transbond Plus Self-Etching Primer (TPSEP). The composites used were Filtek Bulk Fill Flowable (groups I and II), Filtek One Bulk Fill (groups III and IV), Filtek Z350 XT (groups V and VI), Filtek Z250 XT (groups VII and VIII), and Filtek Z100 (groups IX and X). The attachments were molded in a silicone matrix adapted to the buccal area of the teeth, and then light-curing was performed. The samples were stored in distilled water for 24 hours. Subsequently, shear strength tests were performed using a universal mechanical testing machine. The results were analyzed using analysis of variance (ANOVA) and Kruskal–Wallis test and Student's t-test (p = 0.05). Results: There were no significant differences (p = 0.230) among most of the adhesive systems for bonding orthodontic attachments. However, group VII differed from groups II, III, VI, and X (p < 0.05). Conclusion: The Filtek Z250 XT composite on teeth etched with 37% phosphoric acid produced the strongest bond. The bonding was weakest with the Filtek One Bulk Fill composite on teeth etched with 37% phosphoric acid. Clinical significance: With the popularization of aligners, it is necessary to test the materials involved in this treatment modality. Knowing the best material for making the attachments provides a more predictive treatment.