Background and Purpose: Given the urgency to design programs to increase physical activity, especially to combat obesity in children, the primary purpose of this study was to investigate perceptions and opinions of a nature-based physical activity intervention designed for low-income urban adolescents. Methods: Four focus groups of adolescents, ages 11 to 14, were conducted, as well as 5 individual interviews with youth programming experts. Results: Focus group interviews revealed how children perceive the outdoors, including their fears and barriers to exercising outside. Expert interviews discussed the necessity of becoming embedded within a network or working alongside community programs with strong ties to a target community in order to be trusted to carry out such an intervention. Discussion and Translation to Health Education Practice: Health education practitioners can use our qualitative findings in the planning, promotion, design, and evaluation of a nature-based physical activity program. Being cognizant of the fears and previous experiences of urban adolescents, as well as using the advice given by our adolescent and expert participants, should increase a program's ability to successfully recruit and facilitate a nature-based physical activity intervention.