Mental imagery is defined as the mental representation of future events, actions, or tasks. Imagery techniques have been frequently used as means to change behavior. Numerous strategies have been used including guided imagery, mental simulations, and functional imagery training. Several theories explain how mental imagery may change behavior, including social cognitive, emotion regulation, and elaboration intrusion theories. Key mediators of imagery interventions include self-efficacy and outcome expectancies, emotion regulation, cue accessibility, and desires and intrusive thoughts. Imagery interventions are effective in changing behavior, typically with small-to-medium effect sizes. Imagery interventions are more effective in older populations, when detailed instructions are provided, and if they are longer in duration. Practitioners considering using imagery to change behavior should consider (1) imagery intervention content and format; (2) selection of the appropriate target audience; (3) identification of means to promote imagery intervention effectiveness; (4) identification of training and skills required for the type of imagery; (5) the appropriate dose of imagery; (6) inclusion of methods to evaluate imagery intervention fidelity; and (7) means to evaluate the efficacy and theory-based processes of imagery interventions. More high-quality experimental and intervention research evaluating imagery techniques on behavior change in diverse behaviors, contexts, and populations is required.