Thin palladium films of about 100 nm thickness have been successfully deposited on hydrogenated amorphous silicon using an electroless deposition process from palladium-ammine baths. The d.c. magnetron reactive sputtered 18% hydrogenated amorphous silicon (a-Si:H) possessed a hydrogen-passivated surface, necessitating an activation step prior to the electroless deposition to obtain a film with good uniformity. The specially prepared hypophosphite-based dilute metal ion bath exhibited good stability at low operating temperatures of 35-50 °C. The composition and microstructure of the active palladium aggregates were characterized by transmission electron microscopy and energy-dispersive X-ray spectroscopy, while the palladium films deposited from the citrate, NH 3 NH 4 Cl, ethylnediamminetetraacetic acid (EDTA) and triethyleneammine (TEA) baths were examined by scanning electron microscopy. In the activation step, marked differences in morphology and distribution of the palladium aggregates on the activated a-Si:H, a-Si, and crystalline silicon substrates were observed and discussed. The electroless palladium films with higher coverage from the NH 3 NH 4 Cl, EDTA, and TEA baths were more uniform and crack free, while those from the citrate bath suffered from damage due to incorporated hydrogen, resulting in bare spots, microcracks and even local a-Si film peeling. Auger electron spectroscopy revealed that codeposited phosphorus varied from a maximum of 14 at.% in the EDTA bath films to a minimum of 2-3 at.% in the citrate and TEA bath films.