The composition of the cored wires is inhomogeneous and contains solid velum as well as a powder filling which strongly influences the particle formation, in-flight particle behavior, the coating microstructure, and consequently the behavior of the desired coating. To study the effect of particle size distribution of the filling powder in cored wires the parameters of the twin wire arc spraying process such as current, voltage, and atomization air pressure are changed for different intervals of particle size distributions (-45µm+25µm, and -95µm+63µm). Fluctuations in arc voltage and current are measured and found to be higher at smaller particle sizes. The characteristics of inflight particles showed a higher particle velocity in case of smaller particle sizes. The particle temperature is higher in case of bigger particle sizes. The splats tend to form a pancake shape in case of smaller particle sizes. Therefore, the lamellas are more homogenous and the porosity is low. This investigation is important for deep understanding of twin wire arc spraying with cored wires.