Aim: This study aimed to reveal the relationship between changes in Claudin-5 expression and the duration of healing in Achillestendon injury.Material and Methods: 18 Achilles tendons of Wistar-Albino rats were used in the study. Rats were divided into 3 groups as 6 ratsin each group, group 1; sham group, group 2; tendon repair group (sacrificed after 3 weeks), group 3; tendon repair group (sacrificedafter 6 weeks). Immunohistochemically, the tendons were stained with Claudin-5 and the degree of staining with light microscopewas rated between 0 and 3. The obtained scores were compared with Kruskal Wallis test and Posthoc analysis.Results: The scores were 0.5 ± 1 (0-1) in group 1.1 ± 1 (1-2) in group 2 and 1.5 ± 1 (1-2) in group 3. A statistically significantdifference was found between the groups (p = 0.026). In the posthoc analyzes, there was a significant difference between group 1and 3, but there was no significant difference between groups 1 and 2 and between groups 2 and 3.Conclusion: The expression of claudins is regulated by many factors, including hormones, various cytokines, and epithelialmesenchymaltransition-related transcription factors. In this study, the increase in the expression of Claudin-5 was noticed inproportion to the progress of primary wound healing. This relationship may be a part of the repair mechanism. The role of claudinlevels in intercellular passage is crucial for function as it is important for cell signaling. Achilles tendon healing can be attributed toa laboratory parameter such as claudin. This can help to understand the recovery rate and can help early return to work or sport.We believe that as a laboratory parameter Claudin-5 may be useful in the evaluation of tendon healing.