Nickel alloys can be joined reliably by all types of welding processes or methods, with the exception of forge welding and oxyacetylene welding. This article discusses the heat treatment of nickel alloys and tabulates nominal compositions of selected weldable wrought nickel and nickel alloys. It provides information on gas-tungsten arc welding, gas-metal arc welding, plasma arc welding, shielded metal arc welding, and submerged arc welding for welding nickel alloys. The article reviews the defects encountered in the arc welding of nickel alloys, including porosity, cracking, and stress-corrosion cracking. It provides information on the factors that influence the choice of filler metal and welding process of nickel alloys.