OBJECTIVE To compare dyadic (marital) functioning between users of natural family planning (NFP) and users of artificial methods of contraception (AMC). METHODS A cross-sectional study was conducted in healthy, over eighteen-year-old couples living in stable relationships recruited from primary and secondary health centers in Santiago, Chile. Participants were assessed using a structured interview on sociodemographic and sexual aspects. Primary outcome, marital functioning, was studied using the Dyadic Adjustment Scale (DAS). RESULTS One hundred and thirty-eight couples were studied, sixty-nine in each user group. Both groups had a similar average time living together (124.3 vs. 126.9 months). DAS results were consistent with functional couples in both groups, but on average, the NFP group had a significantly higher DAS score than AMC. After controlling for age, socioeconomic status, time in the relationship, and religious commitment in multivariable analysis, the NFP group had a 47 percent (odds ratio = 1.47) greater possibility of having a functional marital score above the cutoff (DAS > 114) when compared with the AMC group. The AMC group reported more frequency of sexual intercourse but similar sexual satisfaction. Most (>60 percent) of the NFP couples mentioned that their methods improved their relationship. CONCLUSIONS There are sociodemographic differences between both groups, explained partly by unequal access to NFP centers. Both groups have DAS scores within functional range, but NFP users have a higher probability of being in that functional range. This study of mentally and emotionally healthy couples highlights the importance of family planning methods on intimate relationships. Summary Marital functioning is affected by family planning methods. A structured interview and a specific inventory to address conjugal functioning were applied to a group of healthy couples who live in stable relationships and are users of natural family planning (NFP) or artificial methods of contraception (AMC). The results were consistent with functional couples in both groups, but on average, the NFP group had a significantly higher score than the AMC group. The use of NFP explained this difference. This study of mentally and emotionally healthy couples highlights the importance of family planning methods on intimate relationships.