["Personal Relationships, Volume 33, Issue 2, June 2026. ", "\nABSTRACT\nSelf‐control determines well‐being in individuals, but also plays an important role in close relationships. However, only few studies investigated self‐control in dyads before. Therefore, from a dyadic perspective, our study aims at better understanding how average levels and differences in two relationship partners' self‐control are related to their personal and relational well‐being in daily life. We evaluate three competing accounts, positing that well‐being in couples might be highest when both partners exhibit (1) complementing (great partner differences), (2) similar (small partner differences), or (3) overall higher levels (high partner averages) of self‐control. To evaluate these hypotheses, 53 mixed‐gender couples (Mage = 24.29 years) individually completed daily diaries across 21 days. Multilevel dyadic score modeling largely showed evidence for Hypothesis 3 (totality): High partner averages in self‐control were related to more positive affect between and within couples, less negative affect and higher overall relationship quality between couples, and more life satisfaction within couples. However, similarity (i.e., Hypothesis 2) in self‐control was related to more closeness within couples. Together, our findings underline the importance of considering different levels of analyses (i.e., individual vs. dyad, between‐couple vs. within‐couple, global vs. specific assessments of psychosocial functioning) when studying self‐control in close relationships.\n"]