Physical inactivity is a health issue with serious consequences for older adults. Investigating physical activity promotion within a multi-theoretical approach may increase the predictive strength of physical activity determinants and facilitate the development and implementation of effective interventions for older adults. This article examines constructs from the Transtheoretical Model, Theory of Planned Behavior, and Self-Determination Theory and their integration with the Stages of Change Model in order to understand physical activity behavior change among older adults. In addition, barriers and facilitators of physical activity are identified. The need for a comprehensive multi-theoretical approach in physical activity behavior change for older adults is reinforced and implications and research areas to be addressed are discussed.