It is commonly believed that intensive English programs (IEP) are designed to immerse learners in an English-speaking environment to help them effectively develop their language skills. Therefore, despite countless studies on the importance of a learner's first language (L1) in second language learning, some IEPs enforce English-only policies that prohibit L1 use both in and beyond the classroom. Knowing students' attitudes toward such policies is essential; however, research says very little to help us understand students' perspectives. Thus, in this study, IEP students of various proficiency levels and L1 backgrounds described their attitudes toward the institutional English-only policy at an intensive English program associated with a large U.S. university. Data were collected through a survey (n = 158), interviews (n = 6), and focus groups (n = 4). Positive attitudes included feeling that the English-only policy helped students to improve their English proficiency, prepare them for the high demands of using English proficiency in real-world interaction, and demonstrate respect for other students and teachers who cannot understand their first language, as well as for other students' learning goals and efforts. Nevertheless, several aspects of the policy were perceived negatively, including the ways teachers dealt with students speaking their L1 outside the classroom, methods of punishment that could impact students' grades, the unconditional character of the policy that denied learners their agency, and the lack of systematic implementation. Based on these findings, suggestions are provided for designing institutional environments that could more effectively maximize target language use rather than demoralize learners.