Background: The mechanism by which social relationships influence health can be interpreted as a social network regulating one's health behaviors. Based on the hypothesis that relatives, friends, or neighbors are sources of social support and may monitor one's health behaviors, researchers have gotten significant and consistent results that a social network can regulate health behaviors. However, few empirical studies have been conducted to examine the role of informal care in the regulation of health behaviors, especially for elderly individuals with chronic diseases that can be controlled by healthy behaviors. This paper researched the effects of informal care on health behaviors-smoking control, dietetic regulation, weight control, and maintenance of exercise-among elderly patients with chronic diseases in China who are facing the challenge of aging. Methods: We used the propensity score matching method to control the impacts of a very rich set of family and individual characteristics. The 2011-2012 national baseline data of the China Health and Retirement Longitudinal Study (CHARLS) was used. Results: Our findings showed that informal care could significantly help improve the health behaviors of elderly people. Informal care could improve the compliance of smoking control and dietetic regulation significantly. Elderly people with informal care smoked less and consumed more meals per day. For weight control, informal care helped decrease the possibility of weight gain of elderly people, but its impacts were not significant for BMI and weight loss. Last, for the elders, informal care could only help increase the probability of walking exercise; however, there was no significant result for moderate exercise. Conclusions: Findings from this study highlight the importance of informal care among elderly people. Our results appeal to policy makers who aim to control chronic diseases that they should take informal care into account and provide appropriate policies to meet the demand of informal care for elderly people.