This article discusses how the category of argumentativeness is employed in online movie reviews written in English. The objectives of the study were to consider the concepts of argumentation and argumentativeness, to define the categories of argumentativeness and evaluativeness as the constituents of a movie review, as well as to identify the lexical-semantic, stylistic, and structural-syntactic parameters of the argumentative discourse expressed in an online movie review. The validity and reliability of the ways used to process the material under study were ensured by the correct application of the following modern methods of linguistic analysis: structural-semantic, interpretative, and functional-stylistic. A number of examples were provided, all proving that the development of the author’s thesis occurs both explicitly (owing to the presence of the thesis and at least two arguments, linking words, introductory phrases, parenthesis) and implicitly (through to the question-answer form of presentation, irony, sarcasm, and using of numerous personal pronouns). The results obtained show that conjunctions play a significant role in the development of the argumentative discourse: firstly, coordinating conjunctions (such as and, so, but) introduce the thesis; secondly, subordinating conjunctions (for example, because, since, as) introduce arguments serving to put forward the thesis. It was concluded that the argumentative discourse in the text of a movie review explicitly manifests itself through such lexical means used to express the category of cohesion (transition from one segment to another while maintaining both structural and semantic unity) as in the first place, for example, then, plus, finally, etc. It was also revealed that any “incorporations” of other discourses, which are markers of a causal interdiscursive strategy, have an argumentative potential in the text of a movie review and fall into two categories: references to the director’s previous works; references to films of other directors. The results of this study are important for developing modern genre studies and the theory of speech acts.