One of the main purposes of foreign language teaching is currently identified by many researchers as developing intercultural communicative competence (ICC) of foreign language learners. Facebook is one of the easiest and quickest ways to communicate with other people, therefore it may potentially be used to promote intercultural communicative effectiveness (ICE), one of the subcomponents of ICC. Within this scope, the aim of this study is to investigate the effect of Facebook on ICE among English as a Foreign Language (EFL) students. A mixed-methods research was employed, the data were gathered from multiple sources including pre- and post-administration of intercultural effectiveness scale, semi-structured interviews, and students' essays. Three conclusions were reached in this study. First, the intercultural instruction had a significantly positive effect on learners' ICE. Second, the discussion on Facebook group had significantly higher ICE scores than the in-class discussion group. Third, most of the students had positive attitudes and feelings towards the intercultural instruction and the use of Facebook for developing ICE.