This manuscript discusses the realization of a measuring system, which monitors elementary composition of the weld seam during aluminum sheet welding. For this purpose, an aluminum sheet is welded to titanium, which is detected by the measuring system if the power of the welding laser is set too high during the welding process of aluminum. This measuring system is based on the principle of laser-induced breakdown spectroscopy (LIBS). A high-energy probing laser is used to irradiate a sample on the surface and a plasma is formed. This plasma emits material-specific characteristic radiation that enables conclusions to be drawn about the elementary composition of the sample. First, the spectra of the metals used in the welding process, aluminum and titanium, were collected by means of LIBS. The investigations showed that there are two peaks of high intensity for aluminum at a wavelength of approximately 395 nm. Titanium, on the other hand, has peaks of high intensity in the wavelength range of approximately 500 nm. For the separate detection of these characteristic peaks, a suitable measurement setup was created. This design allows spectral and temporal separation of the element-specific signals. An aluminum sheet welded to titanium was then examined at right angles to the weld seam in 30 μm steps. The results show an increased signal from the detector for the 500 nm wavelength range, indicating the presence of titanium. These results are supported by additional investigation using energy dispersive X-ray spectroscopy (EDX) and indicate material mixing in the center of the weld seam.