The article focuses on the functioning of dialectal features of phonetics and morphology in the comedies by 16-century Florentine and Siena-born authors (N. Machiavelli, A. Piccolomini, G. Bargagli, G.M. Cecchi, A.F. Grazzini, Intronati Academy members). The way dialectal and normative features are combined in the plays in question can be regarded as a model of how the Italian language, initially codified on the basis of 16-century literary texts and used mainly in writing, was progressively mastering new communicative functions. It is by using the potential of living Tuscan dialects that the Italian language norm gradually overcomes its inevitable artificiality. The 16-century comedies deserve attention on the part of Italian sociolinguistics as a manifestation of ongoing interaction between the evolving standard language and living dialects’ usage.