Laser-welded joints were prepared using moldings of polycarbonate, polyamide-6, and polyamide-6 reinforced with 30% glass fibers. Preparation of thin polished samples of the joints facilitated examination of the laser-affected zone (LAZ). The samples were examined using optical and polarized light microscopy, as well as scanning electron microscopy. The study evaluated the influence of laser power on the geometry and dimensions of LAZ, in both the absorbent and non-absorbent parts of the joints. The results indicated a correlation between LAZ dimensions and the tensile strength of the laser-welded joints. There is evidence of melt and fiber migration in the LAZ.