An important goal of building "age-friendly communities" is to help the elderly to access more opportunities for social participation and better health. However, little is known about the complex relationships between neighborhood environment, social participation, and elderly health. This study examined the mediating role of social participation in the area of neighborhood environment affecting elderly health and explored the discrepancy among different age groups in 43 neighborhoods of Shanghai. Both neighborhood environment and social participation had significant positive effects on elderly health in all the samples. Meanwhile, social participation served as a mediator of the relationship between interpersonal environment and elderly health. Furthermore, remarkably, health promotion effects transferred from the physical environment to interpersonal environment and social participation with age; the influence of physical environment on elderly health decreased with the increase of age, while the influence of interpersonal environment and social participation on the health of the elderly increased with the increase of age. This study found that physical environment, interpersonal environment, and social participation had different effects on elderly health of different ages. Different policies should be applied toward improving the interpersonal environment, optimizing of physical environment, and guiding the community activities.