Critical size tendon defects demand for tissue samples replacing the missing tissue and guiding an effective healing. Autografts, allografts, or xenografts represent viable options; however, limited availability and donor site morbidity go along with this approach, representing big disadvantages. Tissue engineering of tendon tissue is a further strategy fulfilling this need. Basically, an appropriate scaffold material is developed and tested for its biomechanical suitability as a graft material. In addition, cell seeding might improve biointegration of the tissue engineered construct (TEC). Different cell sources as well as different cultivation procedures can be applied in order to tune the envisioned primary strength of the TEC. In this chapter, in vitro fabrication protocols and mechanical tests as well as animal in vivo experiments will be presented—covering various (bio)materials, cell types, and cultivation procedures.