Strategies employed in cross-cultural complements may cause misunderstanding in that they are either overused or under-used. In the literature, these types of misunderstandings have been referred to as pragmatic failure; however, they are mostly explained as cultural differences rather than linguistic ones. The present study looks at the problem of politeness formulas being used in English and Persian from a Relevance Theory point of view. To this end, a set of data collected in a variety of everyday situations were analyzed using the definition of complements for classifying polite expressions. This study attempted to shed some light on such linguistic differences by showing different interpretations of complements in both languages. The data comes from native speakers of English and Persian, both in monolingual and bilingual settings. The monolingual settings were both within and outside Iran, and, therefore the cultural settings were significantly different. The bilingual settings were so selected that they included speakers of both languages from different cultural backgrounds. The variety of linguistic as well as cultural backgrounds of the informants’ data led to quite rich results so that they could be generalized to some extent.