© 2020 ACM.Serious games address not only entertainment purposes but also the transformations on the behaviors of their players. Serious games have recently been used in several domains, such as education, training, rehabilitation, and defense. The positive impacts of the serious games have been highly emphasized in the literature given their strong elements in motivation, a sense of progress, and a sense of purpose. Thus, this study aims to transfer these well-known strengths of serious games to environmental awareness. To do so, a life simulation-like serious game, Save the Planets, has been developed to nurture, care about, and learn from the Solar system. The game also lets the users create their own customized systems so that the aspirations and priorities of the players could be detected. To measure the immediate impact of the Save the Planets serious game, three different scales - -Environmental Identity Scale, Pro Environmental Behavior Scale, and Environmental Action Scale - - were applied in the pre-test and post-test evaluations of the 22 participants. The results show that the Save the Planets serious game significantly changes the pro-environmental awareness, and this serious game may be used to better inform and motivate the participants to take long-term actions.