There is still a major underrepresentation of females in STEM fields, with many girls beginning to lose interest as early as middle school. This is due to a variety of factors including lack of role models, stereotypes, ineffective teaching methods, and peer influence. A popular way to increase female interest is through day camps and other programs where girls complete a variety of activities related to science and engineering. These activities are usually designed around problem-based learning, a student-lead approach to teaching that requires students to work collaboratively and use background knowledge to solve some sort of given problem. In this project, a day camp for middle school girls was created and implemented to increase student interest in STEM through three problem-based learning activities. By analyzing survey data, it was concluded that the camp was successful in increasing interest and changing participants' attitudes towards science. This approach to learning could be applied to other subject areas, including mathematics, to increase the interest of both male and female students at the secondary level.