This research aimed at preparing an out-of-school Science, Technology, Engineering, and Mathematics (STEM) education program for secondary school students and investigating the effects of the program on students' interest in STEM fields. As part of this investigation, this study sought the students' awareness of a career in these fields as well as their comments on the process and the contribution of the process to the 21st century skills. The research was conducted with a mixed methods research design. The participants of the research consisted of 24 secondary school students. The data were collected through STEM career interest survey, STEM perception test, participants' STEM diary, observation, and field notes. The study's out-of-school STEM education program lasted 8 days. This study's findings include students had an increased awareness and perception of building a career in the fields of STEM. It was confirmed that students had fun during the activities, and during the entire process, they made positive comments. Implications from this research highlight how this type of activity may improve the 21st century skills of the students.