In the current study, the effects of particle size on compaction behavior of water-atomized pure iron powders are investigated. The iron powders are assorted into three groups depending on the particle size; 20-45 ${mu}M$, 75-106 ${mu}M$, and 150-180 ${mu}M$ for the compaction experiments. The powder compaction procedures are processed with pressure of 200, 400, 600, and 800 MPa in a cylindrical die. After the compaction stage, the group having 150-180 ${mu}M$ of particle size distribution shows the best densification behavior and reaches the highest green density. The reason for these results can be explained by the largest average grain size in the largest particle group, due to the low plastic deformation resistance in large grain sized materials.