The purpose of this study was to examine the effect of a structured, playful activity program on the development of social skills in kindergarten children during break time in the schoolyard. Twenty eight boys and thirty two girls aged from 5 to 6 years old consisted the sample of the present study. The participants were randomly divided into two groups the treatment and the control group respectively. The experimental group participated in a 4 weeks playful program while control group didn't participate in any kind of structured activity. Data were gathered through observations and videotaped recordings of the students in the schoolyard during breaks. The researcher coded children's behaviours from video recordings and completed the Social Skills Rating System (SSRS) for each child, before and after interventional program. Results demonstrated that there was statistically significant difference between the degree of development in students' social skills during breaks and their participation in a structured programme of playful activities in the schoolyard.