In this study the expressive function of colloquialisms is examined through the lens of linguopragmatics using the material from professional discourse, which is marked by a strict structure of expressing ideas. The study identifies expressive means of influencing the recipient and traces general trends of using colloquialisms in the English-language mass media texts as well as transcripts of business talks held between some major companies. The paper elucidates the concept of linguopragmatics and defines the subject of studies within this discipline, as well as addresses notions of colloquialisms and their expressive function. We have found that colloquialisms are increasingly used in professional discourse. The study provides an overview of the concept of lexical-semantic field, as colloquialisms are mostly actualised at the lexical level. The authors investigate the lexical-semantic field “to invest money” comprised of colloquialisms from English-language mass media outlets, along with colloquialisms used in transcripts of large companies. The following expressive means of producing an influence on the recipient have been found in the texts: bold type, capitalisation of each word, italics, numerals, capitalisation of abbreviations (the graphic level); phrasal words, metaphors, allusions, positive particles, abbreviations, epithets, short forms of nouns (the lexical level); declarative sentences, interrogatory sentences, parcellation, antithesis, parallel structures (the syntactic level). The expressive function of colloquialisms is widely reflected in professional discourse. After comparing the use of colloquialisms in mass media texts and talks transcripts we found that the most frequent expressive means are declarative sentences at the syntactical level and metaphors at the lexical level.