Aluminum alloys, particularly the heat-treatable alloys, are sensitive to weld cracking. Anticipation of these characteristics and general knowledge of these materials assist in selection of suitable method for welding heat-treatable aluminum alloys. This article provides a general description of the metallurgy, characteristics, and applications of heat-treatable aluminum alloys and a detailed discussion on the characteristics of heat-treatable aluminum alloys, their resulting impact on the weld quality and property, along with the methods of avoiding or reducing the impacts. The impact created in the weld quality includes crack sensitivity, liquation cracking, porosity, and heat-affected zone degradation. The article provides an overview of filler alloy selection for reducing weld crack sensitivity and increasing weld strength, ductility, and corrosion resistance in the welds of heat-treatable aluminum alloys.