Creating an effective learning environment in tertiary-level classrooms in Bangladesh can be challenging. The size of the classroom and the atmosphere within it can have a significant impact on the learning experience and outcomes of students. Classroom size is an important factor to consider when creating a space conducive to learning. The study sights on the consequence of ESL (English as Second Language) classroom size and environment at the tertiary level in Bangladesh. The study is qualitative in nature. It is consisted of a review of the extensive literature in the respective field, interviews with twenty English teachers from two renowned private universities in Bangladesh, and the observation of twenty classrooms from those universities. It has been found from the cross-checking of teachers’ interviews and classroom observation that most of the universities do not have suitable classroom size as well as the environment negatively impacted on ESL learners. A classroom that is too small or too large can make it difficult for students to learn effectively. Ideally, class size should be between 25-30 students for optimal learning outcomes. Besides, larger class sizes may require additional materials and resources to ensure that each student has access to the necessary materials. Furthermore, the classroom must be well-lit and ventilated so as to create a comfortable environment for learning. Finally, it is important for teachers to consider the physical layout of the classroom and ensure that it facilitates an atmosphere conducive to effective instruction. By taking these considerations into account, teachers are able to create an environment where students are able to learn effectively and reach their full potential.