Almost sixty percent of adults within the United States are in a married or committed, cohabiting relationship. This study sought to examine the trajectory of relationship satisfaction over 14 consecutive days employing an ecological momentary assessment (EMA) method. Daily reports of relationship satisfaction were collected via a smartphone application developed from the LifeData platform. Phone-based interview questions posed one week after the 14-day EMA period afforded evaluation of usability and acceptability, in preparation for a much larger study of couples coping with cancer. Twenty-seven adults in a married or committed, cohabitating relationship served as participants, recruited from researchmatch.org. (These individuals were not coping with cancer.) Participants received a smartphone notification between 7:30pm and 8:30pm each day, with 45 minutes to begin recording their responses. A single item from the Dyadic Adjustment Scale (item #31) was used to assess relationship satisfaction. Findings revealed a marginally significant increase in satisfaction over the course of 14 days (b = 0.04, t = 1.85, p = .077). In addition, an intraclass correlation (ICC) value of 0.59 indicated larger between-person variability than within-person variability, suggesting that satisfaction varies more from one individual to another than it does within individuals over time. Finally, plots of mean relationship satisfaction by the standard deviation of relationship satisfaction showed lower variability in day-to-day satisfaction among those who were on average more satisfied with their relationship compared to those who were on average less satisfied. Feedback regarding convenience and ease of the application indicated favorable attitudes towards smartphone-based data collection.