This study aims at exploring the teacher's perceptions about comprehensible input on English vocabulary acquisition, their knowledge about it, and the ways they provide it in the classroom. The participants are 10 teachers of English who are teaching General English at a university in the Mekong Delta. A questionnaire was used to collect data from the teachers. The results indicate that the teacher's knowledge of Krashen's hypothesis is quite good. Even though some teachers are unfamiliar with the Input Hypothesis, they still place much value on comprehensible input based on their own teaching experience. However, to raise the quality of teaching English, all the teachers should expand their knowledge and improve their professional development. Krashen’s Hypothesis about comprehensible input should be spread more widely in the education field.