This article presents the design, process of construction, content and validation of the Socioemotional Well-Being Index. This index is a composite indicator of subjective well-being, and has been designed with the aim of providing a measurement device for the sociological analysis of the subjective components of quality of life and social quality. Two spheres of knowledge have been combined in its construction: research in social indicators, the recent development of which has been oriented toward the elaboration of composite indicators, and the theoretical content developed in recent decades by the sociology of emotions. As a composite indicator, the index presented in this article offers a hierarchical and multidimensional alternative to the univariate scales measuring happiness and satisfaction most often used in social research. In addition, in comparison to measures of subjective well-being grounded in cognitive evaluations, this index is based on the evaluation of a series of emotional states recently experienced by individuals. The conceptual definition of socioemotional well-being is based on Thomas Kemper’s social interactional theory of emotions and Randall Collins’ theory of interaction ritual chains. A “4 factor, 10 variable” solution has been obtained by applying common factor analysis to the data of the European Social Survey, 2006.