In this paper, we directly assessed the extent to which the association between religious attendance and the social support trajectories of older Mexican Americans is due to selection (spurious) processes related to personality, health status, and health behavior. We employed seven waves of data from the Hispanic Established Populations for the Epidemiologic Study of the Elderly (1993-2010) to examine the association between religious attendance and perceived social support trajectories (n = 2479). We used growth mixture modeling to estimate latent classes of social support trajectories and multivariate multinomial logistic regression models to predict membership in the social support trajectory classes. Growth mixture estimates revealed three classes of social support trajectories: high, moderate, and low. Multinomial logistic regression estimates showed that the odds of membership in the low support trajectory class (versus the high social support trajectory class) were lower for respondents who attended religious services yearly, monthly, weekly, and more than weekly than for respondents who never attend religious services. Religious attendance could not distinguish between membership in the moderate and high support trajectory classes. These results persisted with adjustments for age, gender, immigrant status, language proficiency, education, income, religious affiliation, marital status, living arrangements, contact with family/friends, secular group memberships, self-esteem, smoking, heavy drinking, depression, cognitive functioning, and physical mobility. We conclude that the association between religious attendance and the social support trajectories of older Mexican Americans is primarily driven by processes related to social integration, not selection.