Pain is one of the most frequent reasons for seeking dental treatment and clinical observations confirm that patients complain of dentinal sensitivity under different conditions and degrees of intensity. This is a very frequent problem after dental restorations with resin composite, even when there is no visible failure in the restoration. The aim of this bibliographic review was to identify the causes of post-operative sensitivity in resin composite restorations and how it can be avoided so that professionals can use this information to reduce the occurrence of this inconvenience in their daily practice. Complete texts of relevant articles on the subject were analysed. There are various causes of post-operative sensitivity in direct resin composite restorations related to failures in diagnosis and indications for treatment and/or cavity preparation, the stages of hybridization of hard dental tissues, insertion of the material, and finishing and polishing the restoration. To avoid or minimize the occurrence of post-operative sensitivity, it is imperative to make a good diagnosis and use the correct technique at all stages of the restorative procedure.