In this research, the impact of physical activities and play on the de-velopment of mental abilities of preschools’ boys was investigated. The participants were 60 Iranian preschool and nursery children selected during the 2005-2006 school year, from the second education district of Tehran preschool and nurseries. They were divided up into experimental (N=30) and control (N=30) groups and their age distribution was 4:3-4:9 and 5:3-5:9 years old . Firstly, a pre-test was administered for both experimental and control groups. After two months of introducing treatments (organized physical activities and plays) to the experimental group, a post-test was administered among both experimental and control groups. In order to see if physical activities and plays could influence the development of mental abilities of preschool’ boys (space perception and body image), three tests, including “draw a man test”, cumulative copied drawings, and cumulative by heart drawings were used. The findings show that the treatments have increased significantly the mental abilities of the experimental group. So, implicitly, we could say that the physical activities and plays can facilitate the development of mental abilities of preschool children.