Abstract: Background and Objective: Type 2 diabetes mellitus is characterized by insulin resistance responsible for the occurrence of various complications. An approach to improve insulin resistance is through consumption of resistant starch type 3 (RS3). A substance that has potential to become RS3 is modified Cassava Flour (MOCAF) made from cassava tubers fermented with lactic acid bacteria. This study assessed the potential of MOCAF and its RS3 to improve insulin resistance in type 2 diabetes mellitus. Materials and Methods: Twenty four diabetes-induced rats were randomly selected and grouped into 4 groups (normal, MOCAF, RS3 and negative control). They were treated with different diets (standard, MOCAF and RS3) as much as 20 g each day for 4 weeks. In the end of study, blood were collected to measure fasting and post prandial blood glucose, plasma GLP-1, plasma insulin and Homeostatic Model Assessment-Insulin Resistance (HOMA-IR).Stool sample were collected from colon for Short Chain Fatty Acid (SCFA) analysis. Data analysis of insulin was performed using one-way ANOVA test, other data analyzed using Kruskal-Wallis. Results: Fasting blood glucose decreased in MOCAF (446-105 mg dL–1) and in RS3 group (494-97 mg dL–1). Post prandial blood glucose decreased in MOCAF (485-136 mg dL–1) and in RS3 group (526- 96 mg dL–1). Significant higher GLP-1 production was found in normal, MOCAF and RS3 groups compare to negative control group (p = 0.004). RS3 consumption stimulated insulin production higher than MOCAF (p = 0.018). HOMA-IR calculation showed normal value in MOCAF and RS3 groups. The SCFA analysis showed that both MOCAF and its RS3 induce the production of valerate beside the three main fatty acids (propionate, acetate and butyrate). Conclusion: This study demonstrated that both MOCAF and its RS3 had the ability to improve insulin resistance in type 2 diabetes mellitus.