This study examined potential pathways in the associations between breastfeeding and mothers' relationship satisfaction, including her satisfaction with father involvement (FI) and parity, among mothers not working outside the home at 6 months. Mothers (n = 222) completed questionnaires at 4 time-points, 3 to 24 months postpartum as part of a longitudinal cohort study. In this study, we were interested in two main outcome variables: mothers' relationship satisfaction with their partner (RS) and continuation of breastfeeding after 3 months. Our first analysis revealed that breastfeeding at 3 months postpartum predicted decreased RS at 6 months postpartum, which was mediated by mothers' dissatisfaction with FI in infant caretaking at 6 months postpartum. These associations depended on mothers' parity: Multiparous breastfeeding mothers were the most dissatisfied with FI. Second, mothers' satisfaction with FI at 6 months also predicted increased RS at 24 months through increased RS at 12 months, but not through FI at 18 months. Third, we found that high dissatisfaction with FI at 6 months was the only significant predictor for the discontinuation of breastfeeding from 3 to 6 months postpartum. Our results suggest that multiparous breastfeeding mothers might be more dissatisfied with FI in caregiving than nonbreastfeeding mothers and primiparous breastfeeding mothers. Furthermore, mothers' satisfaction with FI seems a potent predictor of overall RS up to 24 months postpartum and the continuation of breastfeeding from 3 to 6 months postpartum, regardless of parity. (PsycINFO Database Record (c) 2018 APA, all rights reserved).