The Ancient Greek particle atár has been described as a connective device that encodes either an adversative or a progressive relation between sentences. The purpose of this paper is to revise the description of this particle by framing its analysis within a consistent and theoretically up-to-date model of clause linkage and discourse structure. Starting from previous findings on the function of atár in Homer, I undertake a corpus analysis of atár in Euripides and Aristophanes. This analysis reveals differences in usage at different stages of the language that have been previously neglected. Whereas in Homer, atár largely behaves as a connective and encodes a semantic relation of oppositive contrast between sentences, in later texts it rather behaves as a discourse marker and contributes to the management of both thematic continuity and interactional practices. These differences point to a specific diachronic path of grammaticalization that accounts for the changes undergone by atár.