This study investigates the type of mitigation devices employed by Persian and American native speakers in refusal interactions in a number of formal/informal situations. Twenty two American and thirty Iranian university students participated in four role-play interactions. The production data were supplemented by verbal reports and questionnaires completed by 45 Americans and 50 Iranians to examine speakers’ perceptions of mitigation devices. The results obtained from the analysis of data revealed that, in identical situations, Iranians use more mitigation devices and more specifically make more use of external mitigation devices in comparison to Americans. Moreover, social variables such as social power and social distance made a difference in the way Iranians refused while Americans’ refusals did not change considerably with regard to social variables. It is suggested that foreign language teachers help learners enhance their communicative competence to avoid communication breakdowns which might occur due to inappropriate use of speech acts.