This study focused on K-12 students attending outreach activities (i.e. activities from STEM-based industry emphasizing applications of STEM content in the STEM field), with the main objective being to motivate students for a future career in STEM. Outreach activities can be regarded as environments that extend the regular in-class learning environment and that differ from regular environments in terms of several dimensions, such as autonomy, relevance and learning resources. To date, little research has been conducted on these types of learning environments. We followed a person-centred approach in identifying students' motivational profiles and corresponding student groups in outreach activities, and in evaluating whether students with different profiles differ in their STEM-related attitudes and experience of outreach activities. Both quantitative and qualitative data were collected. Latent-profile analyses revealed four different motivational profiles: good-quality motivation, moderate-motivation, high-quantity motivation and low-quantity motivation. Students with a good-quality motivation reported significantly more favorable-attitudes towards a future career in STEM compared with the other groups, with content and personal relevance being key factors for students with this profile. This study provided support for adding outreach activities to the school learning environment.