•Peak temperature and aspect ratio of weld bead width to depth for aluminum alloy was first time investigated.•Regression models were developed to determine significant parameters.•Positive correlation between laser power and temperature and negative correlation between welding speed and temperature.•Weld bead width was profoundly affected by laser power while peak temperature was influenced by welding speed. This work focuses on the study of parametric effect of laser power and welding speed on peak temperatures, aspect ratio of weld bead width to depth and heat affected zone width for specimens having various thicknesses through transient thermal analysis for AA5083 aluminium alloy. Taguchi array was used to design the experiments to be carried out through Finite Element (FE) simulations which have been carried out with a general purpose commercial FE code, ABAQUS. Results show positive correlation between laser power and temperatures and negative correlation between welding speed and temperature. It is found that the aspect ratio of weld bead width to depth is affected by welding speed while laser power influence the width of heat affected zone. It is concluded that laser power has a significant effect on weld bead width and welding speed has a pronounced effect on peak temperatures.