The researcher examined the psychological factors that influences the physical fitness behavior of adolescents in terms of predisposing factors, enabling factors and reinforcing factors. It also assessed how these factors affect the level of exercise behavior as regards to knowledge, attitude and practice. Data were collected using a self-made survey questionnaire subjected to reliability testing and validation. Data revealed that psychological factors such as predisposing, enabling and reinforcing factors are influential to physical fitness behaviors. Additionally, factors such as knowledge, attitude and practice is affects exercise behavior as to great extent. Hence, as perceived by the respondents, there is “very strong positive correlation” between psychological factors and the level of exercise behavior among adolescents. Results served as a basis for the formulation of physical fitness behavior for a better and positive outlook among adolescents.