The Catholic Church promotes natural family planning (NFP) as a moral means to help couples postpone, prevent, or achieve pregnancy. Past research indicated that many Catholic couples chose artificial contraception rather than NFP, despite being introduced to NFP in marriage formation, which includes the classes that couples take prior to being married in the Catholic Church. Data are limited concerning why couples choose not to practice NFP or how NFP relates to couples’ relationship functioning and their dyadic spirituality. Drawing on data collected from two studies in separate dioceses (one urban and one rural), this article examined the usage rates of NFP, predictors of use, and the effects of NFP on relationship functioning and spiritual intimacy. Results indicated that older age and having cohabited prior to marriage predicted less likelihood of using NFP, while viewing marriage as sacred and shared Mass attendance indicated higher likelihood of NFP use. Furthermore, using NFP predicted higher spiritual intimacy for couples as well as higher relationship satisfaction. Couples’ increased exposure to NFP as a result of premarital education did not impact their decision to use NFP in marriage.