Introduction: A long-term diabetic retinopathy will cause an increase in several growth factors expression like Transforming Growth Factor β (TGF-β). This multipotent cytokine is involved in the process of endothelial cell proliferation. Therefore, this study aims to observe the relationship between TGF-β1 levels in serum and vitreous fluid of Proliferative Diabetic Retinopathy (PDR) patients given Pan Retinal Photocoagulation (PRP) laser therapy. Method: This was a cross-sectional study involving 14 patients with PDR. TGF-β1 levels of vitreous and peripheral blood were measured using Enzyme-linked Immunosorbent Assay (ELISA) method. The data were statistically analyzed using SPSS software for Windows ver. 23.0 for Mann-Whitney and the Spearman correlation test. Results: Our subjects consisted of 57.1% males with a mean age of 51.8 years, where dyslipidemia was the most common comorbid disease. Mean serum TGF-β1 level was 12,821.43 ± 5,253.16 pg/ml, while the mean value in vitreous was 3,692.86 ± 333.89 pg/ml. Meanwhile, there was no significant difference in serum and vitreous TGF-β1 levels between subjects with and without PRP laser therapy (p>0.05). Conclusion: There was no significant correlation between TGF-β1 levels in proliferative diabetic retinopathy patients with and without panretinal photocoagulation laser therapy. However, there was a decreasing trend in TGF-β1 levels in the vitreous fluid, indicating that PRP laser therapy has a positive effect on preventing the formation of neovascularization in the eye.