The robotics curriculum is one of the most common and popular curricula for stimulating students’ interest in the science, technology, engineering, and mathematics (STEM) disciplines. The purpose of this study was to develop a robotics curriculum that highly integrates STEM and uses open software and hardware, and to test its effects on high school students’ learning outcomes, interest, and perceptions of STEM. The study involved 82 Grade 10 students; divided into two groups, the experimental group experienced an integrated robotics STEM course, whereas the comparison group participated in a curriculum with commercial robotics. After a semester, the quantitative and qualitative data showed that the experimental group reported significantly more positive perceptions of integrated STEM, with strengthened knowledge, interest, and career orientation towards related fields. The findings of this study provide suggestions for STEM curriculum development.