Titanium alloys have been attractive due to a high ratio of strength to weight as well as good corrosion resistance. However, strengthening causes a decrease in ductility in Ti alloys, as is usual in other alloys. For enhanced strength without ductility reduction, grain refinement and tensile properties were investigated as functions of thickness reduction of cold rolling and annealing condition in Ti-15V-3Cr-3Sn-3Al alloy with a ${eta}$ single phase. The average grain size of the specimen, which was cold-rolled by 90% and annealed at 700$^{circ}C$ for 5 min, was decreased to approximately 19 ${mu}m$. The grain refinement of 63 μm to 19 ${mu}m$ increased yield stress by 90 MPa without a significant decrease in total elongation. The Ti-15-3 alloy exhibited very low work hardening during tensile test at a crosshead speed of 2 mm/min. This result was discussed based on dynamic recovery associated with dislocation annihilation in grain boundaries.