For better or worse, relationships have the potential to affect individuals' self‐concepts; however, currently no integrative model exists to explain the variety of these self‐concept changes. We propose that self‐concept changes occur along two independent dimensions: direction (increase vs. decrease in content) and valence (positivity vs. negativity of content). These two dimensions combine to create four processes of relationship‐induced self‐concept change: self‐expansion (increasing positive content), self‐contraction (decreasing positive content), self‐pruning (decreasing negative content), and self‐adulteration (increasing negative content). Using community and university samples, we developed a measure of self‐concept change (Study 1) and examined how the four self‐processes were associated with love (Study 1), relationship quality (Studies 2 and 3), and infidelity (Study 3). The self‐concept improvement processes (i.e., self‐expansion and self‐pruning) were associated with greater love and relationship quality, whereas in Study 3 self‐concept degradation processes (i.e., self‐contraction and self‐adulteration) predicted infidelity.