Many studies have investigated students' attitudes toward engineering (ATE), but few have examined the changes in attitudes after attending an engineering design curriculum. This study analyzes these attitudinal changes in students attending an engineering-focused science, technology, engineering, and mathematics (EF-STEM) curriculum and investigates the influence and correlation between attitudes and learning performance. The participants included 364 tenth-grade students (ages 16-18 years). An 18-week experimental intervention design (2 h per week) was adopted. The Attitudes Towards Engineering Scale--Taiwan was applied before and after attending the EF-STEM course; remaining assessments were conducted post-course. The results showed that the ATE statistically decreased after attending the course, shifting from a positive attitude to a neutral-leaning attitude. Although most students appreciated the importance of engineering design, they exhibited a high degree of anxiety toward it. Moreover, their pre-ATE was significantly correlated with their perception of engineering design and learning performance. These results indicate that engineering design curricula do not necessarily have a positive effect on student ATE.