This study considers welding of Ti-6Al-4V, which is widely used in the chemical, automotive, aerospace and medical industries due to its high strength-to-weight ratio and corrosion resistance. Bead-on-plate melt on 2.15 mm thick plates with a 1 kW single mode fibre laser and a continuous wave 4 kW Nd:YAG laser are investigated and compared. The fibre laser was found to produce narrower welds with finer microstructure using less than 30% the laser power required by the Nd:YAG laser. However, levels of porosity were generally higher meaning the Nd:YAG laser welds were classified as higher quality according to American Welding Standard D17.1:2007. In both cases there was a trend for lower porosity at a higher laser power when the welding speed was higher. The difference in porosity levels may have been partly or wholly due to the different inert gas shielding systems used.