Vocabulary knowledge is very crucial for learners who want to be competent in a language. Vocabulary knowledge means having the knowledge of or command over words of a language and their usages in real-life contexts. Vocabulary knowledge can be gained incidentally and intentionally. The paper compares the effectiveness of the reading-only condition and reading-while-listening condition in incidental vocabulary acquisition. It seeks to find out whether students acquire more vocabulary knowledge by reading a text only or reading the text while listening to it. It also disseminates the effect of word exposure frequency. By applying four vocabulary tests, it proves that learners can gain vocabulary knowledge in both the conditions; but the reading-while-listening condition can result in more gain of vocabulary knowledge. The paper also shows that the more the number of encounters with words in context, the more the vocabulary gains. Studies with students from different levels of education and gender based studies can be conducted. This is a pioneering study on this topic in Bangladesh, so the paper will pave a way for the researchers who want to work on the same topic.