Understanding how communication processes contribute to well-functioning versus distressed couple relationships has relied largely on brief, laboratory-based conversations. Harnessing technological advancements, the present study extends the literature by capturing couples' naturalistic communication over one full day at Time 1 (T1). This study tested associations between data-driven categories of couple communication behaviors and relationship outcomes (i.e., relationship aggression, satisfaction, and dissolution) at Time 2 (T2), approximately 1 year later. Emerging adults in different-gender dating couples (n = 106 couples; 212 individuals; Mage = 22.57 ± 2.44; M relationship length = 30.49 months ± 24.05; 72.2% non-White) were each provided a smartphone programmed to audio record approximately 50% of a typical day. Interactions between partners were transcribed and coded for location, activity, affect, and a range of positive and negative communication behaviors for each partner. Even after controlling for T1 assessments of the relevant outcome, one's own hostility and one's partner's hostility at T1 were each positively associated with T2 relationship aggression and negatively associated with T2 relationship satisfaction. One's own withdrawal at T1 was positively associated with T2 relationship aggression perpetration, whereas one's partner's withdrawal was negatively linked to relationship satisfaction at T2. One's own playfulness, unexpectedly, was linked to lower subsequent relationship satisfaction. Withdrawal increased the likelihood of relationship dissolution, whereas warmth and playfulness decreased the likelihood of dissolution. The relevance of couples' ordinary, everyday communication for meaningful relationship outcomes is discussed. (PsycInfo Database Record (c) 2024 APA, all rights reserved).