Language is the most important part of human communication. People use language to share their thoughts, feelings, ideas, and problems. In order to be more effective and interesting, languages are rich in various expressions. One of the most interesting ways of expressing is by using idioms. An idiom is an expression or “a set phrase of two or more words that means something different from the literal meaning of the individual words” (The American Heritage Dictionary of Idioms). Idioms make languages more expressive and therefore, they make an important part of both English and Croatian. Taking that into consideration, this research is based on the analysis of idioms with proper names in the English language and their equivalents in the Croatian language. It is based on a corpus which consists of 30 randomly selected phraseological units from various dictionaries. The thesis is divided into five major parts. The first part is an introduction that briefly explains how the research itself was conducted. The second part discusses some basic theoretical terms that are important for the understanding of this research. The third part explains how the analysis itself was conducted. The most important part is the fourth one which includes the analysis of 30 chosen idioms with proper names in English, as well as their equivalents in Croatian. If there is no equivalent, a paraphrase for the idiom will be provided. The fifth, and last, part is the conclusion that sums up the whole research by explaining the significance and the role of idioms in both English and Croatian language.