The microstructure of sputtered thin films of platinum, deposited on glass substrates in the presence of argon, is investigated by x‐ray diffraction. (111) layers tend to align parallel to the substrate surface and the degree of orientation depends on the film thickness, deposition rate, gas pressure, and cathode potential. These parameters can be optimized to give maximum orientation or crystallinity. From an analysis of the breadths of the (111) and (222) reflections by the variance and Fourier (Warren‐Averbach) methods and from peak asymmetries, the domain size, strain, dislocations density, and faulting probability are obtained for as‐prepared and annealed films. It is found that annealing decreases the strain due to dislocation. Large domain sizes with low fault and dislocation densities occur at high deposition rates and low pressures, and structural perfection is greatest when the ratio of the deposition rate to the pressure is in the region of 2000 A˚ min−1Torr−1. It appears that some annealing due to particle bombardment takes place during deposition.