When do people express their emotions to other people and when do they choose not to do so? Emotional experience-positive or negative-often leads people to reveal their feelings to others, especially to close relationship partners. Although emotional expression has been incorporated into recent dyadic models of emotion regulation, little research has examined the specific interpersonal processes responsible for facilitating or inhibiting emotional expression. This article reports results from a pair of methodologically distinct studies examining the impact of perceived partner responsiveness (PPR) on emotional expression. The results of Study 1, a 2-week daily diary study, demonstrated that within-person variations in the perceived responsiveness of a close partner were associated with corresponding day-to-day variations in emotional expression to that partner. In Study 2, in the context of a stressful situation, we manipulated perceptions of a romantic partner's responsiveness and then measured emotion expression toward that partner. Higher levels of experimentally induced PPR causally led to greater expression of anxiety. Together, these studies identify PPR as an important interpersonal mechanism underlying emotional expression. (PsycINFO Database Record (c) 2019 APA, all rights reserved).