Laser welding of similar or dissimilar, high-reflective metallic thin foils ranging from 10 to 50um is very challenging. Those ultra-thin metal foils are very sensitive to heat and deformation easily occurs due to its light weight and heat-induced surface tension during the process. Ideally, a good process requires high peak power to achieve high absorption coupling efficiency and as low as possible the average laser power or total energy applied on foil to minimize the heat impact. Ns pulsed fiber lasers operate at pulse energies of just a few microjoules to >1 mJ, affording pulse durations in the 10–1,000 ns range, and are capable of peak powers of >10 kW and operation up to 4 MHz, thus significantly differentiating them from conventional lasers such as continuous wave (CW) and even quasi-CW (QCW) long-pulsed lasers, however many also operate in these regimes.. In this paper, we report a similar Aluminum metallic foil weld (25um and 50um thickness) and its dissimilar weld with a copper foil of thickness of 10um by a SPI G4 ns fiber laser. Those welded samples have very smooth weld bead with no intermittent bead and little distortion. The measured tensile strength of the welded foil ranges from 2.5N to 25N depending on foil thickness.