This thesis observes problems that arise when translating background onomatopoeia in manga from Japanese to Croatian. The thesis aims to identify the most common translation techniques used in translation of onomatopoeia in manga, to analyse the advantages and disadvantages of each technique, and to identify problems that arise during translation. This thesis consists of a theoretical overview of onomatopoeia in Croatian and Japanese, the use of onomatopoeia in manga, and an overview of translation theory as well as the most commonly used translation techniques for translating onomatopoeia, followed by a quantitative and comparative analysis of onomatopoeia taken from six manga comics in Japanese and their translations into Croatian. Identified onomatopoeias are categorized according to writing system and type of onomatopoeia, and the used techniques for translation and visual adaptation. The most common script and onomatopoeia type are identified, as well as translation and visual adaptation techniques, for which advantages and disadvantages of each were also briefly explained. Finally, the thesis identifies problems that arise in the translation of onomatopoeia, and lists some ways of solving or avoiding them. In conclusion, the problem of translating onomatopoeia in manga is a problem of visual as well as textual adaptation, since the appearance of the translated words is as important for the reader's impression as the quality of its translation. In a large number of analysed data, it was noted that preference was given to the visual impression rather than translation of the meaning of the word, and in many examples the translation was completely omitted. Also noted is a combination of formal and dynamic equivalence, where the manga is at the same time adapted to the Croatian reader, but also aims to ensure that the reader is always aware that they are reading a Japanese manga. The necessary knowledge and skills necessary for quality translation of onomatopoeia in manga have also been identified, mainly good understanding of onomatopoeia and sound-symbolic system of both Japanese and Croatian.