Abstract: Idioms, based on the Pederson’s (2005) view, were considered as culture-bound elements. Therefore, idioms’ problems were discussed as a sort of cultural problems basedon the cultural losses’ categorization of Hanada Al-Masri (2010). Regarding Newmark’s (1988) view about the existing deficiency in translation and Nord’s (1991) view about lack of a common translation code for all cultures, the aim of this research was to provide a platform to discuss the deficiencies of translating idioms in cultural context and to get the translator general theory in translating idioms by the means of Naturalness theory. The researcher applied qualitative-quantitative methods in conducting this research by means of direct observation of source language idioms and their Persian translation. Based on the findings, the researcher found that complete loss, the loss of symbolic value and figurativeness of idioms, was the most rated phenomenon and the explicit loss, the loss of a cultural counterpart, was the least rated one. Also it was found that the translator general theory was to deliver a natural translation and to turn unfamiliar idioms into familiar words and idioms in order to make the translation acceptable and understandable.