Dissimilar metal joints of TiNi shape memory alloy wire and stainless steel wire were welded by laser welding method with and without Co filler metal. Comparative microstructure and properties of laser welded joints with and without Co filler metal have been detailed investigated. The effects of Co filler metal thickness on joint microstructure and properties were also discussed. The results indicated that the addition of Co filler metal had great effect to improve joint microstructure and properties. When 20μm thick Co filler metal was used, the joint tensile strength and elongation reached the maximum values (347MPa and 4.2%), and the corresponding joint fracture mode changed from pure brittle feature to mixture of cleavage and dimples due to decreasing brittle intermetallic compounds such as TiFe 2 , TiCr 2 , etc. But excessive Co addition resulted in decreasing the joint properties because of forming more Co–Ti intermetallic compounds.