Nickel-titanium alloys are among the most frequently used shape memory alloys for highly functional products due to their distinctive properties such as shape memory effect, superelasticity and biocompatibility. As a joining process for manufacturing components made from these alloys, laser welding has become well established and has been extensively investigated in the past with regard to its influences on alterations of properties and microstructure. However, in the field of welding sheet metal semi-finished products, these studies were focused almost exclusively on conventional dimensions, while investigations on welds for micro applications – for example for the important field of microelectromechanical technology – have so far been largely ignored. Based on methods of design of experiments, the authors of this contribution have therefore carried out studies on the micro-welding of Ni55/Ti45 foil with a thickness of 125 µm with a fibre laser in a but-welding configuration and were able to demonstrate that optimal results of weld seam strength were achievable with an oscillation of the laser beam, which have not been investigated so far. The effect of the oscillation of the laser beam on the welding result was therefore systematically investigated and obtained results are described and discussed in this contribution. A circular oscillation was chosen for the experiments and amplitude and frequency were varied in the range of 0 - 0.2 mm and 0 - 2000 Hz respectively, at selected speed of the laser beam movement and power. Analyses of the microstructure with different microscopic techniques showed slightly distinct alterations in grain growth during solidification, segregation development and structure of the heat-affected zone due to the oscillation, and nanoindentation tests demonstrated variations in mechanical-technological properties along the weld seam.