Introduction:Diabetes mellitus is a metabolic disorder characterized by persistent hyperglycemia due to defect in insulin secretion, insulin action, or both. In the condition of diabetes disruption of the wound healing process such as traumatic ulcers, one of which is caused by a decrease in several growth factors such as TGF-β1. This study was aimed to determine the effect of allogenic Freeze Dried – Platelet Rich Plasma (FD-PRP) topical application on TGF-β1 expression in traumatic oral ulcers of Wistar rats suffered with diabetes mellitus (DM). Methods: Allogenic FD-PRP was obtained from 35 healthy Wistar rats (Rattus novergicus) and gel was made by adding 2% carboxymeth-yl cellulose (CMC). Another 30 Wistar rats were divided into 6 groups and induced with 50 mg/kg streptozotocin as diabetogenic agent that selectively damage pancreatic B cells. Traumatic ulcers were made by touching a heat burnisher on lower labial mucosa. Traumatic ulcers in 3 control groups were given 2% CMC and the other 3 groups were given topical application of allogenic FD-PRP gel. The expression of TGF-β1 was observed on day 3, 5 and 7 by immunohistochemical examination. Data were analysed using SPSS program with ANOVA test with the results of the study were considered significant if less than 0.05. Results: The results showed a higher increase in TGF-β1 expression in the group given allogenic FD-PRP than in the control group. Analysis of variance showed significant differences (p <0.05) of TGF-β1 expression between the treatment and control groups. Conclusion: Allogenic FD-PRP increases TGF-β1 expression during the healing process of traumatic oral ulcers in diabetic Wistar rats. Thus, TGF-β1 has a crucial role in healing process of diabetic oral ulcer.