Wood, JessicaQuinn-Nilas, ChristopherMilhausen, RobinDesmarais, SergeMuise, AmySakaluk, John2026-05-052026-05-052021-02-16https://doi.org/10.1371/journal.pone.0247001https://hdl.handle.net/10012/23209© 2021 Wood et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Intimate and sexual relationships provide opportunity for emotional and sexual fulfillment. In consensually non-monogamous (CNM) relationships, needs are dispersed among multiple partners. Using Self-Determination Theory (SDT) and dyadic data from 56 CNM partnerships (112 individuals), we tested how sexual motives and need fulfillment were linked to relational outcomes. We drew from models of need fulfillment to explore how sexual motives with a second partner were associated with satisfaction in the primary relationship. In a cross-sectional and daily experience study we demonstrated that self-determined reasons for sex were positively associated with sexual satisfaction and indirectly linked through sexual need fulfillment. Self-determined reasons for sex predicted need fulfillment for both partners at a three-month follow up. The association between sexual motives and need fulfillment was stronger on days when participants engaged in sex with an additional partner, though this was not related to satisfaction in the primary relationship. Implications for need fulfillment are discussed.enAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/emotionssurveysheterosexualsmental health and psychiatryhomosexualssocial psychologygender identityqualitative studiesArticle