The place of culture in teaching English as an international language (EIL) has been so far of great concern among specialists in the area of language teaching; therefore, the representation of culture in English language teaching materials should reflect this important issue. The current study is intended to examine the representation of culture in the locally developed EFL ‘Prospect’ textbook series employed in Iranian Junior high school. The study engages teaching English as an international language (TEIL) and Cultural Semiotics adapted by Dinh (2016) as the theoretical and analytical frameworks to explore culture across texts, visuals and tasks. The conversation sections of Prospects 1, 2, and 3 including texts, visuals provided in student book and tasks provided in teacher's guide went undergone investigation. The outcomes of the research reveals that 1) culture is evident in both implicit and explicit manners in texts and visuals; however, it is limitedly represented in the tasks, 2) cultural diversity has not much been attended to; in-depth levels of culture belonging to ‘small’ c categories and socio-cultural awareness are neglected, 3) local Islamic-Iranian culture is dominant specifically across visuals, while other countries' cultures are minimally represented, 4) there is occasional detached mismatch between texts and visuals, and 5) most questions require students to comprehend the conversations or visuals at linguistic and information layers, while speculative and comparative questions addressing socio-cultural contents of language use are extremely limited. The findings of the study will be advantageous to the curriculum developers, and EFL practitioners in Iran and some recommendations for future textbook writers are suggested.