Japanese is a language rich in onomatopoeic and mimetic words, words that mimic sounds and other phenomena with their form. They are an integral part of the language and are used in nearly all situations, they also pose their own peculiar challenge to both learners and translators of Japanese. This study examines the Japanese onomatopoeic and mimetic words in the novel Sensei no kaban by Hiromi Kawakami, and their translations in its Finnish translation, to determine what techniques are most commonly used and why? As Finnish is also said to have a rich onomatopoeic and mimetic vocabulary, the frequency at which these terms are translated into equivalent onomatopoeic or mimetic words is also examined. The results show that the majority of the Japanese onomatopoeic and mimetic words, most of which function as adverbs, are translated as adverbs or verbs or they are completely omitted. Exactly a quarter of the examined cases have been translated using onomatopoeic or mimetic words, most of which are verbs.