BACKGROUND AND OBJECTIVES: Falls among older adults is a pressing public health challenge. Considerable research documents that longer tai chi courses can reduce falls and improve balance. However, longer courses can be challenging to implement. Our goal was to evaluate whether a short 6-week modified tai chi course could be effective at reducing falls risk if older adults designed a personal home practice plan to receive a greater tai chi ‘dose’ during the 6 weeks. DESIGN: A 3-city wait-listed randomized trial was conducted. Habituation Intention and Social Cognitive Theories framed the ‘coaching’ strategy by which participants designed practice plans. RE-AIM and Treatment Fidelity Frameworks were used to evaluate implementation and dissemination issues. Three advisory groups advised the study on intervention planning, implementation, and evaluation. To measure effectiveness, we used Centers for Disease Control and Prevention recommended measures for falls risk including leg strength, balance, and mobility and gait. In addition, we measured balance confidence and executive function. RESULTS: Program Implementation resulted in large class sizes, strong participant retention, high program fidelity and effectiveness. Participants reported practicing an average of 6 days a week and more than 25 min/day. Leg strength, tandem balance, mobility and gait, balance confidence, and executive function were significantly better for the experimental group than control group. CONCLUSION: The tai chi short course resulted in substantial tai chi practice by older adults outside of class as well as better physical and executive function. The course reach, retention, fidelity, and implementation across 3 cities suggest strong potential for implementation and dissemination of the 6-week course.