This study examined the effects of group games on female elementary students' cooperation skills. Two classes of elementary female students were assigned as an experimental or a control group. The study used a quasi-experimental method for the evaluation and comparison of cooperation development and administered the Measurement of Competitive-Cooperative Attitudes (Martin & Larsen, 1976) to gather data. A T-test was done to examine the hypothesis. A pre-test was performed to measure cooperation skills development and see whether they are comparable. Then, the experimental group played the selected group games, while the control group continued the previous curriculum. A middle test was conducted after 6 weeks. There were no meaningful differences between the groups. As it was predicted that time would be a factor that affected the results, the program continued for another 6 weeks. Finally, a post-test was conducted, revealing that group games can increase cooperation skills (p< 0/05).