Production of Zirconium alloys for nuclear power reactor comprises of a number of steps during swaging and each step influences microstructural and mechanical properties of the finished product. The Zircaloy-4 was subjected to cold swaging to reduce its cross section gradually from 23 to 16 mm diameter via several passes of swaging followed by intermediate vacuum annealing at 732 °C for 3 h. EBSD was carried out to study the influence of twinning in the Zr-4 alloy. Twinning is observed in swaged ({112¯$\overline{2}$2}〈112¯3¯$\overline{2}\overline{3}$〉) and annealed ({112¯$\overline{2}$1}〈112¯6¯$\overline{2}\overline{6}$〉) samples. TEM was done to substantiate the role of dislocation density. It is observed that several swaging and annealing treatments have improved tensile strength and fracture toughness of the Zr-4 alloy.