Objectives: Our study aimed to investigate whether EndoMT contributes to fibrosis in DD by analyzing the expression of endothelial and mesenchymal markers, as well as an EndoMTrelated TF, in the palmar fascia of DD patients and healthy fascia. We hypothesized that in DD patients, the endothelial cells of the palmar fascia would exhibit decreased expression of endothelial markers and increased expression of mesenchymal markers and the EndoMTrelated TF. Material and methods: Palmar fascia samples were collected from patients with DD and carpal tunnel syndrome, after which they were processed through fixation, dehydration, paraffin embedding, and sectioned for histological and immunofluorescence analyses. Hematoxylin and eosin staining, along with immunofluorescence staining for endothelial and mesenchymal markers, were performed on these sections, followed by digital image analysis to quantify the fluorescent signal. Two-way ANOVA with Tukey9s post hoc test was used to assess for statistically significant differences in protein expression between sample groups. Results: Immunofluorescence analysis revealed that the expressions of endothelial markers vWF and CD31 were significantly decreased, while the expressions of the mesenchymal marker vimentin and EndoMT-related TF SNAI2 were significantly increased in the endothelial cells of samples obtained from patients with DD compared to healthy controls. These changes were observed in both fibrotic cords and adjacent macroscopically unaffected palmar fascia, with more pronounced alterations in fibrotic cords. Statistical analyses confirmed that the observed differences in protein expression between sample groups were significant. Conclusions: Considering the downregulation of endothelial markers, upregulation of mesenchymal markers and the expression of SNAI2, EndoMT is likely present and contributes to the fibrosis in the palmar fascia of DD patients. These changes were also found, albeit to a lesser degree, in macroscopically unaffected fascia, indicating that EndoMT occurs there as well. The presence of EndoMT in macroscopically unaffected fascia could explain the higher recurrence rates in less extensive surgical procedures and therapies targeting EndoMT could reduce clinical recurrences.