A binder composition for use in making metal parts via a metal powder injection molding process containing the following components: (a) a first polymer with a relatively low solubility parameter such as polyethylene and polypropylene; (b) a second polymer with a relatively high solubility parameter such as polystyrene and poly(methyl methacrylate); and (c) a block copolymer containing blocks of the first and second, or other structurally similar, constituting monomeric units. Examples of the block copolymers include ethylene/styrene copolymer, propylene/styrene copolymer, and isoprene/styrene copolymer, etc. The binder composition is dispersed in an appropriate dispersant, such as an oil or wax, then blended with a metal powder to form a metal powder injection composition. The metal powder injection composition forms a green compact with a predetermined shape and dimension using an injection molding machine. Finally the green compact is sintered to form the final product. The present binder composition eliminates the incompatibility problem which is often encountered when using multi-component binders; this allows the green compact to maintain excellent dimensional and physical integrities both before and during the sintering step and thus ensures the precise dimension of the final products.