A heterogeneous catalyst consisting of AuPd nanoparticles dispersed on titanium oxide was synthesized by a colloidal route. The diameters of these nanoparticles range from 1 to 5 nm, as determined from scanning transmission electron microscopy (STEM) images recorded with a high-angle annular dark field detector (Z-contrast method). Bright field images obtained on an aberration-corrected STEM show the structure of the oxide support and the metal particles with high resolution. This microscope allows to record secondary electron images that provide supplementary information about the morphology of the support crystals and the localization of the particles on them. The combination of the images with the spectroscopic investigation of selected points and areas is of particular importance. Herein, efficiently collected energy-dispersive X-ray spectra give evidence for the formation of an AuPd alloy in the nanoparticles. This result is confirmed by the results of X-ray absorption spectroscopy (EXAFS) studies.