Background: Tendon lesions are frequently caused by trauma in both humans and animals, including horses, and can result in lameness. Tendons are not very good at mending. In order to enhance tendon regeneration and healing, tissue engineering approaches have been introduced. This study shows how to heal Achilles tendon lesions in rabbits using mesenchymal stem cells (MSCs) generated from adipose tissue in conjunction with a collagen–hyaluronic acid scaffold. This procedure can be enhanced by the application of stem cells and biological scaffolds. Methods: Fifteen mature white New Zealand healthy rabbits (۲۰۰۰-۳۰۰۰ grams) were randomly allocated into three groups (n=۵). In each rabbit, Achilles tendon ۳mm lesions were induced. molecular scaffold of collagen (۹۰%) and hyaluronic acid (۱۰%) produced, and adipose tissue containing MSCs isolated from the rabbit's shoulder region (stem cell presentation approved by CD۲۹ and CD۹۰ markers). (Group ۱): injured the tendon bio-scaffold (collagen + hyaluronic acid) without MSCs implanted. (Group ۲): Injured the tendon bio-scaffold (collagen hyaluronic acid) with MSCs implanted. (Group ۳): Injured without bio-scaffold (collagen hyaluronic acid), MSCs were implanted with fibrin sealant as a carrier. After ۸ weeks, rabbits were euthanized, and tendons were Histopathologically scored based on eight criteria: extracellular matrix (ECM) organization, cell-to-matrix ratio, cell alignment, cell dispersion, tenocyte nuclear morphology, repair tissue organization, vascularization, and inflammation. The scoring system was slightly modified from the method described by Stoll et al. (۱۹۹۹). Results: H&E staining showed that in the healed tissue of group ۲, the nuclei of newly generated cells were similar to heterochromatic nuclei of tenocytes (p-value<۰.۰۵). While in groups ۱ and ۳ the similarity is less than the previous group, also in group ۲, the ratio of cell to matrix in regenerative tissue is much more than in healthy tendons. The extracellular matrix in group with bio-scaffold+MSCs was significantly improved than group ۳. Conclusion: A collagen-hyaluronic acid scaffold with adipose-derived MSCs in the regeneration of tendon lesions in white New Zealand rabbits was meaningfully effective.