In order to increase idiomatic competence in students, it is necessary to teach idiomatic expressions. Teachers or students must have knowledge of the factors that influence idiom mastery to improve learning of these idioms. One of the main objectives of this study is to determine the types of idiomatic expressions and translation strategies which a translator will use in translating the idiomatic expressions they find. This study uses qualitative methods to obtain information and data in order to obtain conclusions with descriptions based on verbal and non-numerical data as the basis for analyzing research problem solving. Researchers performed several data collection techniques in this study. Researchers read, mark, select and classify the data found. Mona Baker's theory is used in this research. Mona Baker thinks that translation strategies are applied when the translator has difficulty and wants to solve a problem. Therefore a translator will produce a good translation. There are 4 translation strategies according to Mona Baker's theory which are used to translate idiomatic expressions contained in the novel Lord of the Flies; The same meaning and idiom form (9.26%), idiom-like meaning and form (22.92%), translation by paraphrasing (66.82%), and translation with omission (0.97%). in the novel Lord of the Flies, there are six types of idiomatic expressions that have been classified according to Charles Hockett's theory; substitution (0.0%), personal name (7.8%), abbreviation (0.97%), compound (26.34%), compound words (28.29%), slang (36.58%) . regarding the formulation of the problem and the purpose of this study. Both of these illustrate the types of idiomatic expressions found in William Golding's Lord of the Flies and the translation strategies used by the translator, Dhewinerta Hardjono, in translating idiomatic expressions found in the entire novel.