This chapter introduces the work of the economics and sociology of conventions (EC/SC) applied to labor issues. Also, the chapter emphasizes the essential place of labor in the EC/SC program. Its main concepts, notions, and hypotheses have emerged from the study of labor-related issues or have found in these issues a fertile ground for decisively proving their relevance: in particular, investments in form, the negotiation and interpretation of rules, the social construction of qualification, trials as devices of social hierarchization, the legitimacy constraints on conventions, and the power of valorization. The aim of this chapter is to present the main features that characterize the work of the EC/SC in the field of labor. First, work is systematically considered as a productive activity and thus analyzed in relation to different firm configurations. Second, the quality of work is not a natural given; it is the result of a social and equipped process of evaluation, subject to legitimacy constraints. Finally, the chapter presents how three main EC/SC models are used to conceptualize the plurality of labor conventions.