Discourse and media communication researchers pay attention to the fact that popular discursive and communicative practices have a tendency to hybridization and convergence. Discourse which is understood as language in use is flexible. Consequently, it turns out that one and the same text can represent several types of discourses. A vivid example of this tendency is revealed in American commencement speech / commencement address / graduation speech. A commencement speech is a speech university graduates are addressed with which in compliance with the modern trend is delivered by outstanding media personalities (politicians, athletes, actors, etc.). The objective of this study is to define the specificity of the realization of polydiscursive practices within commencement speech. The research involves discursive, contextual, stylistic and definitive analyses. Methodologically the study is based on the discourse analysis theory, in particular the notion of a discursive practice as a verbalized social practice makes up the conceptual basis of the research. This research draws upon a hundred commencement speeches delivered by prominent representatives of American society since 1980s till now. In brief, commencement speech belongs to institutional discourse public speech embodies. Commencement speech institutional parameters are well represented in speeches delivered by people in power like American and university presidents. Nevertheless, as the results of the research indicate commencement speech institutional character is not its only feature. Conceptual information analysis enables to refer commencement speech to didactic discourse as it is aimed at teaching university graduates how to deal with challenges life is rich in. Discursive practices of personal discourse are also actively integrated into the commencement speech discourse. More than that, existential discursive practices also find their way into the discourse under study. Commencement speech also embodies didactic discourse as its objective is to share the final piece of knowledge the teachers can offer on such a significant day. Besides institutional and didactic discourses, commencement speech represents memoire discourse for many orators go back to and indulge in their memories of the days passed. Apart from this, current commencement speeches are closely related to ironic discourse. As a result of three types of transformations discursive practices undergo in commencement speech discourse it acquires the property of a polydiscursive hybrid. The harmonious combination of polydiscursive practices contributes to commencement speech hybridization which increases the degree of commencement speech persuasiveness.