This study is a case study which aims to find out students’ perception on the use of WhatsApp in writing activity. This qualitative study was conducted at SMP N 3 Tanah Abang Pali with four students as the participants taken from ninth grade students by using maximum variation sampling. In collecting data, interview with 13 questions was used to explore their opinion on the use of WhatsApp in learning writing. Thematic analysis was used to analyze the data. The findings from the students’ interview found that there were some perceptions about the use of WhatsApp in writing activity. The first one was advantages of using WhatsApp in writing activity. The advantages of WhatsApp were Through WhatsApp the teacher can give direction to students in writing activities, Easy to access, Perceived Progress of Vocabulary. For the disadvantages of Costly to use, Internet Connectivity, Obsessed with WhatsApp, in a group. Keywords: Students perception, WhatsApp, writing activity