Code-switching is a term used for conscious transition from one language to another and this occurs in situations when another person also knows the language (Prebeg-Vilke, 1991). Similar definition is also given by Jelaska (2005) which states that bilingual speakers often use code-switching, i.e. transfer from one language to another within the same speech situation or even sentences. Various research proved that code-switching is a phenomenon characteristic for bilingual and multilingual speakers and largely depends on sociolinguistic factors, which is also a first aim of this work – identification of conditions in which code-switching appears. The second aim concerns correlation of the child's exposure to the Croatian language and the increase of size and number of utterances in the same. The third one concerns the errors made in each language. Over the four month period speech production of the trilingual child was recorded. All sound files were conducted through CLAN program where they were also transcribed and encoded (MacWhiney, 2000) within the CHILDES (Child Language Data Exchange System) database. Subsequently, all data were processed in Microsoft Excel (2010) and SPSS (2016). The results confirmed the importance of sociolinguistic factors, especially the role of interlocutor. Unfortunately, no correlation has been found between increased exposure to Croatian language and increase of utterances in Croatian due to various study limitations. The greater number of mistakes was found in English where her language development is far more advanced compared to Croatian whose production is reduced to the insertion of a single word in the syntax of the English language. Errors in English are mostly morphological while in Croatian phonological. Despite weaker language knowledge in Croatian, the child has excellent communication with all the people surrounding her so we can see a high level of communication competence. Although not all the results confirmed the literature references, they offer good guidelines for further researches of speech production of bilingual and multilingual children.