**Abstract**

Multipotent mesenchymal stromal cells (MSCs) are a promising therapeutic tool to treat tendon disease. Aiming to establish successful treatment approaches and to fully exploit the regenerative potential of the MSC, it is crucial to understand their mechanisms of action. However, these can be multifaceted and strongly context-sensitive and are still not well-understood in the context of tendon disease. This review aims to shed light on the different possible mechanisms, including engraftment, tenogenic differentiation, extracellular matrix synthesis and remodeling, immunomodulation, pro-angiogenetic effects, trophic support, and protection of resident tendon cells. Evidence from experimental and clinical (veterinary) case studies was compiled and interpreted in conjunction with the respective in vitro and animal models used.

**Keywords:** MSC, ASC, progenitor cell, tendon, mechanism of action, engraftment, differentiation, extracellular matrix, remodeling, immunomodulation, trophic support
