In this work an attempt is made to study the effect of heat input in CO2 laser welding of Ti-6Al-4V Plates. Ti-6Al-4V alloys finds wide range of applications in aerospace and biomedical industries owing to their properties such as high strength to weight ratio and very good corrosion resistance. Welding plays an important role in the fabrication of components made of Ti-6Al-4V. In this work, Ti-6Al-4V plates of thickness 3 mm was welded in butt joint position. Laser welding was done at different heat inputs by varying the laser power and keeping the welding speed at a constant value. The quality of the weld was analysed with respect to bead geometry, mechanical properties such as microhardness and Tensile strength. It was understood that, with increase in heat input, mechanical properties got increased. The reasons for the variation of the properties are also discussed with the help of metallurgical analysis.