With the rapid development of Internet techniques in China, more and more Chinese middle-aged and older adults have begun to use the Internet for their daily social interactions, and the resulting online social capital may affect their health. Using data from the Chinese General Social Survey of 2017 (n = 7733, aged 45–90 years old), this study investigated the influence of online social capital on the health of middle-aged and older adults in China, and the Heckman sample selection model was used to address potential sample selection bias in ...