To increase engagement with science and technology, young people around the world are encouraged to attend activities at science centers. But how effective are these activities? Since women have weaker ability beliefs and interest in technology than men, it is especially important to learn how science center visits affect them. In this study, we tested if programming exercises offered to middle school students by a Swedish science center would increase ability beliefs and interest in programming. Students in grades 8 and 9 (n = 506) completed a survey before and after visiting the science center, and their ratings were compared to a wait-list control group (n = 169). The students participated in block-based, text-based, and robot programming exercises developed by the science center. The results showed that programming ability beliefs increased for women, but not men, and that interest in programming decreased for men, but not women. The effects persisted at a follow-up (2-3 months). The young men reported stronger ability beliefs and interest than the young women at all timepoints. The results imply that science center activities can make programming feel less hard, but adaptations may be needed to also increase interest.