Yb-doped CdO thin films with different Yb contents were prepared on glass and silicon substrates by vacuum evaporation technique. The effects of Yb-doping on the structural and optoelectrical properties of the host CdO films were systematically studied. The X-ray diffraction study shows that some of Yb3+ ions substituted for Cd2+ and the solubility of Yb in CdO is very limited and may be around similar to similar to boolean AND boolean AND boolean AND.2 at.%. The Yb-doping influences all the optoelectrical properties of CdO. The bandgap of Yb-doped CdO suffers narrowing by about 20% with a very small (0.03 at.%) doping level. The electrical behaviours show that all the prepared Yb-doped CdO films are degenerate semiconductors. Their dc-conductivity, carrier concentration, and mobility increase compared with undoped CdO film. The largest mobility of about 87 cm(2)/V s was measured for 0.13 at.% Yb-doped CdO film. From transparent-conducting-oxide point of view, Yb is sufficiently effective for CdO-doping.