In recent years, cold spraying has attracted worldwide interest for the fast deposition of high-quality metallic coatings. In this process, particle velocity is one of the key parameters for a successful deposition upon impact. Many investigations have examined the particle acceleration behavior through numerical simulation. However, there are few papers concerned with the measurement of in-flight particle velocity. In the present paper, the velocities of the cold spray particles were measured by a developed diagnostic system based on thermal radiation used for thermal spray particles. A laser power was also employed owing to the extremely weak thermal radiation of the cold particles. The particle velocity was also estimated using the developed simulation model, which is based on a two-dimensional axisymmetric mathematical model. The measured results were compared with the calculated ones under different spray conditions. The comparisons show that the measured results agree well with the calculated ones. The proposed measurement method in this paper is reliable. On the other hand, it is confirmed that the developed simulation model can predict accurately the particle acceleration behavior in cold spraying. The optimization of the cold spray process can be conducted following this simulation model.