The purpose of this study was to develop a theoretical understanding of what could influence exercise adherence in physically non-active young women. Interviews with twelve physically nonactive young women were strategically selected and analyzed by grounded theory. The results were that several factors could influence exercise adherence in physically non-active young women, and that these factors can be regarded as a number of interrelated dimensions. The influence was coming either from the exercise or from the environment connected to the exercise. The participants wanted to feel enjoyment and to learn something during the exercise (recreation/learning influence). They also wanted to feel belongingness during the exercise (social influence). An influence that promotes health or builds skills (investment influence) could be a trigger to start exercising among the participants, but not to maintain exercise adherence. Influence coming from the environment (enabling influence) was both important and stimulating for physically non-active young women in establishing regular exercise. It is important to present the model developed in this study to communities, sports federations and other authorities working with health promotion activities so that they can explore innovative ways to promote exercise adherence among physically non-active young women. Good examples could be to offer non-competitive sports as well as to develop well-designed exercise programs for physically non-active young women.