The issue of population aging is of great concern to all countries in the world, and China is one of the countries with more serious population aging. Under the situation of increasingly serious population aging, we should pay more attention to the life of the elderly after retirement. Paying attention to the health behavior and living conditions of the elderly population will contribute to the process of successful aging. Retirement is a critical point, and the transition period will have different effects on the health of the retired population, with some literature suggesting negative effects on the health of individuals after retirement, and others suggesting positive effects on health. Retirement has caused a lifestyle change in older adults, and few studies have addressed the impact of retirement on individuals’ choices of specific healthy lifestyles, particularly the impact of retirement on physical activity participation. In this study, we used data from the 2015, 2017, and 2018 China Social Tracking Survey (CGSS) to explore the effect of retirement on individual male physical activity participation using the sample size of retired male individuals from the three data periods and using the IV-Probit model. The results showed that retirement had a significant positive effect on individual men’s physical activity participation. In terms of the influence mechanism, physical health, psychological health, active learning during leisure time, and Internet use of retired individuals may be the main reasons for increasing physical activity participation. It provides a channel for China to encourage and support older adults to expand their physical exercise participation after retirement and improve their physical and mental health and to promote the shift of older adults’ postretirement lifestyle toward an active and healthy lifestyle.