The oxide dispersion strengthened (ODS) Steel is one of the candidate structural materials for Gen. IV fission systems and fusion DEMO reactor because of its excellent elevated temperature strength, corrosion and radiation resistance. To fabricate these advanced nuclear systems with huge and complex structure, bonding and welding is one of unavoidable issues. Thus, suitable bonding and welding techniques need to be developed with such a process that the microstructures with very small grain size and distribution of nano-oxide particles are not remarkably changed. Transient liquid phase bonding (TLPB) is a potential joining technique to minimize the disruption of these unique microstructures. In this study, TLPB was performed to join ODS ferritic steel blocks using an amorphous inset material based on Fe-3B-5Si compositions with high vacuum hot press. The relationship between microstructure and mechanical properties were investigated. Cross sectional microstructure in joint region were observed by electron microscopy. To evaluate mechanical properties in the joint region, tensile test was also conducted. Although the TLPB ODS steel had good tensile strength, it showed lower elongation than before the bonding.