People in relationships frequently rely on their romantic partners for support through life’s everyday stresses and strains. While the past several decades of research have clarified many of the ways in which support transactions can be both beneficial and harmful to recipients, we lack a comparably clear understanding of the factors that enable or hinder effective support provision in everyday life. The current project addressed this gap by explicating the role of daily emotions and emotion-related processes in the facilitation of social support between romantic partners. Specifically, the study aimed to determine whether 1) partners’ similar daily negative emotional experiences yield better or worse daily support quality, and 2) whether a person’s ability to accurately perceive the day to day negative emotion states of her or his partner can enhance the quality of daily enacted support. Using a 14-day daily diary design with 60 romantic couples, I found that each romantic partner’s daily negative emotional experiences differentially predicted how much support they provided to each other, as well as the visibility of that support and the matching of that support to their partner’s needs. Daily negative emotional experiences also predicted partners being dissatisfied with the support they received. However, when partners felt similarly negative and when they accurately perceived each other’s negative emotions, the negative effects of mood on support quality were mitigated. The results suggest that the joint experiences of emotions matter in determining the extent to which social support quality is undermined by day to day negative emotionality.