Background: Interpersonal emotion regulation is a crucial skill that underpins the emotional dynamics in couples' relationships. In regulating interpersonal emotions, couples not only focus on their own emotions but also consider the emotions of their partner. Objectives: The study aimed to explore the role of interpersonal emotion regulation in couples' relationships. Methods: This qualitative study utilized a grounded theory strategy. Married women and men from Yazd (2021) who met the inclusion criteria participated in semi-structured interviews conducted through purposeful sampling until theoretical saturation was achieved. A total of 20 individuals (13 women and 7 men) were included in the study. Data were analyzed using MaxQDA 2020 software. Results: Collecting and coding the data with the Strauss and Corbin method, as open, axial, and selective coding, gave us 229 open codings, 32 axial codings, 7 selective codings, and one nuclear or core category under the title of safe attachment. The major categories included: Personal development, emotional safety, emotional self-awareness, empathic attunement, comprehensive support, comprehensive improvement of quality of life, and promotion of the spousal-safe base. A paradigm model was drawn from the components of the central phenomenon, causal conditions, contextual conditions, intervening conditions, strategies, and consequences. Conclusions: The specification of effective factors in the formation of interpersonal emotion regulation and the research paradigm model enables the accurate identification of strategies for interpersonal emotion regulation and their consequences in couple relationships, facilitating the progression of couples towards safe attachment. It is suggested that family counselors and therapists use these results to help couples.