Objectives: In this study, we examined Japanese older adults' health habits (healthy diet, exercise, and nonsmoking) using 4 models: sensitive period, pathway, social mobility, and cumulative effects. Methods: A representative cross-sectional survey of people 65 years and older, living in Tokyo, produced 739 effective respondents. Health habits in social networks over the life course, at junior high school, age 20, and age 40, were measured through retrospective recall questions. Ordinary regression and logistic regression were used separately to analyze healthy diet and exercise/nonsmoking. Results: Regarding pathway effects, standardized coefficients of indirect health habits in social networks on late-life health habits were healthy diet = .073 (p < .05) and exercise = .125 (p < .001). Regarding social mobility effects, standardized coefficients of change to poorer health habits in social networks over the life course on late-life health habits, compared to maintaining healthy habits were healthy diet = -.121 (p < .01) and exercise e= -.235 (p < .05). Regarding cumulative effects, standardized coefficients of no exposure to better health habits in social networks over the life course were healthy diet = -0.103 (p < .01) and exercise = -.395 (p < .01). Conclusions: Three models - pathway, social mobility, and cumulative effects - may explain how healthy diet and exercise in social networks over the life course influence these health habits in later life.