This study aimed to examine an effectiveness of uneven-sided games in a third year elementary school invasion ball game units, focusing on the netgame, which is a type of basketball mainly played by women around the UK. The lesson attempted to enhance a decision making ability of the players in a position of a ball through 3-on-1 uneven games and a space creation ability of the players out of a position of a ball through 3-on-2 uneven games. As a result of the lesson, the players with a ball made better decisions to pass a ball to an unmarked team member, which verified the effectiveness of this case study lesson. Besides, the players without a ball utilized a large space to be unmarked, which showed an improvement of the space creation ability. The characteristics of netball, as a teaching material, was also verified its efficiency. Future studies are expected to investigate and solve problems of invasion games, in terms of pupils' developmental stages and tasks in class.