Fixed prosthodontic therapy is based on the production of a fixed prosthesis retained on teeth and/or implants. Complications of fixed prosthodontic and implant prosthodontic therapy are divided into biological and technical complications. Biological complications in tooth-supported prosthesis include caries of the tooth, loss of tooth vitality, changes in the gingiva and periodontium, and tooth fracture. In implant-retained prosthesis, biological complications relate to soft tissue complications and peri-implantitis. Technical complications of fixed prosthodontic and implant prosthodontic therapy include loss of retention, chipping or fracture of ceramics, and fracture of the basic structure. Additionally, in implant-retained prosthesis, a common technical complication is loosening of the implant screw. Complications in fixed prosthodontic therapy can occur at every stage of the production of a fixed prosthesis. To prevent complications, both the clinical and laboratory stages of production should be properly executed. Also, the patient's attitude towards therapy and the maintenance protocols are very important. The aim of this paper is to define possible complications of a fixed prosthetic therapy and to point out the causes of complications with the aim of their prevention.