Classroom interaction plays a significant role in facilitating learners’ development of communicative competence by making input more comprehensible to learners and maximizing the language input to become learners’ intake (Krashen, 1987; Swain, 1995; Long, 1996; Gass, 1997; Lucha & Berhanu, 2015). Results of related studies reveal a low level of communicative competence of many Vietnamese learners of English, which could result from the lack of opportunities for interaction in Vietnamese EFL classes (Hiep, 2007; Ngoc, 2010; Canh, 2011; Ngan, 2013; Tuyen, 2013; Duy, 2014). This study aims to investigate EFL teachers’ challenges in maximizing classroom interaction. A questionnaire was administered to 50 lecturers from sixteen colleges and universities in the Mekong Delta of Viet Nam to examine their challenges in maximizing classroom interaction. The results of the study show that Vietnamese EFL lecturers encountered challenges related to physical factors or learning conditions, learners’ factors and teachers’ factors as well. Learner-related factors showed to be most significant challenge in this study.