The primary goal of the current study was to investigate whether romantic relationship status predicts levels of, and changes in, emerging adults' emotional experience over time. Romantic relationship status has been associated with adolescents' daily emotional experience, in that those in romantic relationships reported more extreme positive and negative emotions. Given that emerging adulthood in contemporary industrialized societies is an emotionally vulnerable time and that romantic relationships become more intimate and important across adolescence through emerging adulthood, it stands to reason that emerging adults' daily emotional experience may be influenced by their romantic relationships as well. There is little research about emerging adults' daily emotional experience, and less about individual-level predictors that may predict its variability. Thus, the current study was designed to address this gap in the literature and do so in a way that provides a thorough description of self-reported daily emotional experience over time: by exploring the experience of individual emotions in addition to overall affect scores, investigating differences in group mean levels, and charting growth trajectories for individual differences in between and within person emotional variability across time. Given extant research findings that females and males report emotional experience differently, sex of respondent was considered as well. Twenty-six days of the self-reported emotional experience of 25 female and 24 male predominantly White 18--20 year olds were analyzed using multi-level modeling. Results reveal that being in a romantic relationship, as compared to not, is associated with a different pattern of growth over time in the individual emotions of contentment and joy, and in the emotion composite of positive affect. Additionally, being in a romantic relationship is associated with higher group mean levels of anger. No mean level differences were found between females and males, regardless of romantic relationship status, in self-reported emotional experience. This study uncovers the complex association between emerging adults' romantic relationship status and emotional experience, revealing the importance of individual differences in understanding the trajectories of various negative and positive emotions over time.