Objectives: The purpose of this study was to investigate whether motivational climates have a differential impact on adolescent psychological and physiological stress responses (i.e., salivary cortisol). It is important to investigate this relationship, as psychological stress and stress-responsive hormones have been implicated in a variety of biochemical processes deleterious to mental and physical health. Although youth consistently respond positively to caring, task-involving (C/TI) physical activity settings, ego-involving (EI) climates remain prevalent in youth sport contexts. Design: Middle school students (N = 47) were separated by gender and randomly assigned to either a C/TI or EI 30 min instructional juggling session. Method: Salivary cortisol was measured at four times over the 3 h study, including one baseline (t = 0 min; juggling session start) and three response measures (t = +30, t = +45, and t = +60 min). Psychological stress and motivational responses were also examined, including anxiety, affect, enjoyment, and effort. Individual items were utilized to substantiate stress perceptions and assess psychological responses. Results: Results revealed El climate procured a significant rise in salivary cortisol and greater humiliation, self-consciousness, shame, negative affect, and anxiety, relative to the C/TI group, while adolescents in the C/TI group responded more favorably (e.g., greater effort and enjoyment). Conclusions: These findings suggest the motivational climate can differentially impact adolescents' stress responses, with EI climates eliciting both physiological and psychological stress responses in youth. In contrast, C/TI climates may buffer performance related stressors that accompany group achievement settings and yield a protective response. (C) 2017 Elsevier Ltd. All rights reserved.