Metastable β Ti-Nb-Sn alloys with low Young's modulus were heat treated after cold rolling to refine microstructures and thereby to strengthen the alloys without sacrificing the low Young's modulus. Alpha double prime (α") martensite with the orthorhombic structure is stress-induced by cold rolling and preferential rolling textures are evolved during a large rolling reduction. Rearrangement of martensite plates parallel to the rolling direction, which is associated with α" rolling texture, leads to a decrease in Young's modulus. Reverse martensitic transformation is almost completed upon heating to 523 K, resulting in very fine β grains elongated to the rolling direction. A high density of dislocations and fine α precipitates are included in the β grains. Low Young's modulus and high strength are simultaneously attained by controlling heat treatment processing parameters. A preliminary experiment showed that a round bar of β Ti-Nb-Sn alloy can be die-forged at room temperature into a stem-like shape for an artificial hip implant.