Migrant students tend to underperform in Science, Technology, Engineering, and Mathematics (STEM) subjects and are less likely to pursue higher education in STEM when compared with their nonmigrant peers. Given the substantial increase in migration, this disparity has been a central concern in science education in many European countries. The purpose of this study was to investigate the effectiveness of an innovative science outreach program that brings together migrant students and STEM professionals with the same linguistic and cultural backgrounds. The program consists of one‐off workshops that follow an inquiry‐based approach and include hands‐on activities and science communication in the students' heritage language. Using surveys with adapted scales and open‐ended questions, we applied a randomized block design with waitlist control groups and repeated measures. Eighty‐three Portuguese‐speaking migrant students aged 6–17 years participated in the workshops in Germany and the United Kingdom. Results indicate that both the students and STEM professionals evaluated the program positively and that students who participated in the workshops tended to demonstrate an increase in their attainment value for science and an increase in their self‐concept of ability for the heritage language 4 weeks after the intervention when compared with students in the control condition. These effects were particularly pronounced for students with low prior motivation to study science or speak the heritage language. Our results thus show that it is possible to foster migrant students' attainment value for science and increase their self‐concept of ability regarding the heritage language through a brief science outreach intervention.