The 1.3 mm thick plate of ODS high temperature alloy MGH956 was TIG welded with fillers containing different B₄C (0, 0.25 and 0.5 mass %), then the effect of B₄C content on the microstructure and mechanical properties of the weld joints was investigated. The results show that the microstructure of the weld metal with B₄C exhibits mainly equiaxed grains, which are fine and uniform, without significant agglomeration of oxide dispersoids, while the strengthening particulates of the alloy distribute in both grains and grain boundaries. The microstructure of weld joint was finer as the filler with B₄C content in a range from 0.25 to 0.5 mass%. However nearly almost the strengthening particulates of the alloy concentrate in the grain boundaries but disappear in the grains for the weld joints by filler with 0.5% B₄C. The tensile strength of the weld joints firstly increases and then decreases when the B₄C content of the fillers ranged from 0% to 0.5 mass%, but their toughness decreases with the induce of B₄C. The tensile strength of the weld joint with filler material containing 0.25% B₄C is the highest i.e. 630 MPa, reaching 87.5% of the parent material. The fractured surface exhibited characteristics of brittle fracture.