This study explored the science, technology, engineering, and mathematics (STEM) attitudes and self-efficacy of secondary students identifying as Black South African, multi-racial or Afrikaans South African, or Botswana, Namibia and Zimbabwe nationals who participated in a non-formal STEM education camp programme. Using Bandura's social cognitive theory for self-efficacy and attitude, this study sought to document participants' STEM self-efficacy and attitudinal factors related to the camp experience. Survey data were collected before and after participants' participation in the camp and a delayed post-measurement after 18 months of exposure. Results indicated a significant increase in the self-efficacy concept of "conceptual understanding" over time between the pre-test and delayed post-test; however, there were no indicated differences over time for the other self-efficacy constructs of "Higher Order Cognitive Skills," "Practical Work," "Everyday Application" and "Science Communication." Analyses of the STEM attitude constructs showed differences between the "Twenty-first Century Skills" (increase over time from pre-test to delayed post-test) and "Your Future" (decrease over time from pre-test to delayed post-test) constructs with no differences for "Mathematics," "Science" and "Engineering and Technology." Furthermore, there were no detected differences of self-efficacy and attitudes from pre-test to post-test. These findings suggest that participating in a singular, non-formal STEM learning event may not be sufficient to document changes in self-efficacy and attitudes from the pre- to post-learning experience; however, the experience could have been one of many learning events that may have provided an opportunity for supporting South African students' self-efficacy and attitude growth, especially in "Conceptual Understanding" and "Twenty-first Century Skills."