This study was a case study which aimed to find out the students’ perceptions on the use of WhatsApp in writing activities at SMA Nurul Ilmi Palembang. This qualitative study was conducted at SMA Nurul Ilmi Palembang with six students as the participants taken from seventeen students using maximal variation sampling. In collecting the data, the interview with 16 questions was used to know the students perceptions in writing activities. Thematic analysis was used to analyze the data. The findings from the interview with the participants found that the perceptions that students perceived during writing activities were students conveyed that WhatsApp was useful for writing activities because WhatsApp made the students flexible for doing the tasks. WhatsApp also was cheap to be used since it did not large data package and the connection was relatively good. WhatsApp potentially improved the students’ vocabulary too through chatting in group and reviewing peers’ task. However, WhatsApp also limited the students writing organization because the students still faced difficulty in organizing a writing especially in determining and elaborating the topic. In addition, the students also felt their grammar did not get improved by writing activities through WhatsApp. It was because the students faced difficulty in understanding the right structure of the sentence especially when the teacher rarely comment about grammar during writing activities through WhatsApp.