Assessment is related to measuring students’ knowledge about the materials which have been taught. Essay is one kind of assessments which is often used in English language Education Department of one private university in Yogyakarta. This research is conducted to find out the students’ perception on essay as a tool to evaluate their learning process, the benefits of essay-based assessment, and problems faced by the students in creating essay. This research used a descriptive qualitative research design and an interview was used as the data collection method. The researcher interviewed four students batch 2015 from different classes at English Language Education Department of one private university in Yogyakarta. The result showed that there are three perception on the use of essay as assessment to evaluate learning process. Students considered that essays are challenging, effective to evaluate writing skill and effective to evaluate students’ understanding on the subject. There were seven benefits of essay as assessment. The benefits were improving vocabulary, improving grammatical skill, improving writing skill, increasing critical thinking, improving knowledge, fostering interest in reading, and becoming more motivated to learn. In addition, there were five problems of essay assessment. The problems were word choices problem, limitation of words, hard to find reference, demand to master material, and challenge to make a good quality essay. In conclusion, essay is an effective tool to evaluate students’ knowledge, although, the xii students feel that essay is challenging because the benefits of essay are more than the problems faced by the students.