Although numerous studies suggest that religious involvement is associated with better health and longer life expectancies, it is unclear whether these general patterns extend to cellular aging. The mechanisms linking indicators of religious involvement with indicators of cellular aging are also undefined. We employed longitudinal data from the 2004 and 2008 Health and Retirement Study, a national probability sample of Americans aged 50 and older, to test whether average telomere length varied according to level of religious attendance. We also tested several potential mechanisms. Our results showed that respondents who attended religious services more frequently in 2004 also exhibited fewer stressful events, lower rates of smoking, fewer symptoms of depression, and lower levels of C-reactive protein in 2008. Respondents who increased their level of attendance from 2004 to 2008 also exhibited lower rates of smoking in 2008. Although religious attendance was not directly associated with telomere length, our mediation analyses revealed significant indirect effects through depression and smoking, but not stressful events or C-reactive protein. We conclude that religious attendance may promote telomere length indirectly by reducing symptoms of depression and the risk of smoking. There was no evidence to support stressful events or C-reactive protein as mechanisms of religious attendance.