The article is devoted to studying the types of modifications of phraseological units with mythological allusions. The functions performed by them in the English discourse are characterized. The relevance of the study is due to the insufficient knowledge of intentionally modified precedent units - phraseological units with a mythological component - and the specifics of their functioning in the discursive space of the English language. The novelty of the study is seen in the explicitation of the modifications (transformations) classification of precedent units in relation to phraseological units containing mythonyms that refer to ancient Greek myths. The author identifies three main modification types of the precedent units of phraseological units with a mythonym component: semantic, structural-lexical and syntactic. Particular attention is paid to identifying the functions of modified phraseological units in multi-discourse English texts. It is shown that the modification of the considered precedent units allows the author of the statement to originally identify the situations and events illuminated by him (the qualifying function of the modified phraseological units), give the text expressiveness and brightness (expressive-decorative function), convincingly express his point of view (persuasive function), convey irony or create humorous effect through a language game (human function), identify their group affiliation (password function).