The elastic moduli and flow stresses of as-deposited Pt and Pt-Ru solid solution thin films were investigated by the nanoindentation method. The influence of solid solution alloying was explored by depositing Pt-Ru solid solution thin films with various compositions onto Si substrates. The 200 nm films were prepared by DC magnetron cosputtering with a Ru composition range from 0 to 20wt%. As expected, the modulus and the flow stress both increased significantly with an increase in Ru. The experimental results compare favorably to predictions based on a simple dislocation motion model consisting of three strengthening terms: substrate constraint, grain size strengthening and solid solution strengthening.