Interpersonal emotion regulation occurs when people influence others' emotions (extrinsic regulation) or turn to others to influence their own emotions (intrinsic regulation). Research on interpersonal regulation has tended to focus on how people regulate emotions, with little interrogation of why people do it, despite the importance of motives in driving emotion regulation goals and strategy selection. To fill this gap, we conducted a systematic exploration of interpersonal emotion regulation motives, employing a participant-driven approach to document the breadth of motives that people hold across different social contexts. Study 1a (N = 100) provided an initial qualitative examination of motives for both intrinsic and extrinsic interpersonal emotion regulation. Study 1b (N = 399) quantitatively catalogued these motives in recalled social interactions. Study 2 (N = 200), a daily diary study, used the motive taxonomy generated in Studies 1a and 1b to understand why people regulated their own and others' emotions in everyday social interactions over the course of 14 days. Together, our findings reveal the diversity of intrinsic and extrinsic interpersonal emotion regulation motives and open avenues to further explore motives both as a precursor to and an outcome of regulatory processes in daily life. (PsycInfo Database Record (c) 2024 APA, all rights reserved).