Relationship difficulties are common during the transition to parenthood and may persist for years. Strategies that enhance couples' daily relational experiences early in the parenting years may serve a protective role. In general, engaging in a capitalization attempt (i.e., sharing personal good news) with one's romantic partner and perceiving the partner to be responsive are associated with better relationship outcomes among committed couples. However, it is unknown whether these relational benefits extend to the early parenting years or to other relational domains such as coparenting, which plays a central role in family functioning. The current study examined same-day associations between couples' capitalization process and relationship closeness and perceived coparenting support in a dyadic context during the first year of parenthood. A subsample of primarily non-Hispanic White coresident mixed-gender couples who participated in a randomized controlled trial of a transition to parenthood program (N = 141) completed daily diaries at 10 months postpartum for 8 consecutive days. On days when mothers shared, both partners reported greater closeness. On days when fathers shared, mothers reported greater closeness and perceived coparenting support. Furthermore, perceived partner responsiveness was associated with greater closeness for both partners and greater coparenting support for fathers. Fathers also perceived greater closeness and coparenting support on days when mothers shared about the child. Findings highlight the potential benefits of capitalization in early parenthood for both closeness and perceived coparenting support and suggest that capitalization may be a low cost, high yield strategy for enhancing new parents' daily relational experiences. (PsycInfo Database Record (c) 2022 APA, all rights reserved).