The fact that English is the second and most frequently taught foreign language worldwide has prompted many researchers to investigate the difficulties faced by language learners. Several previous studies examined students' perceptions of feedback. However, previous studies have only focused on one type of feedback either Grammarly or teacher feedback. This research was conducted to describe both in one study used in argumentative essays. Researchers used a qualitative approach with a single case study design. Three participants were taken because they had passed three writing courses from the first until the third semester. In the first and second semesters, they only used the teacher's feedback. In the third semester, they used the Grammarly Application and got feedback from the teacher. Also, the participants are those who have an excellent grade (A) between 80-100 in argumentative essay writing in the third semester. To collect data, researchers used semi-structured interviews and document analysis. The interview session was conducted for 20 minutes. The researcher also divided the interview session into two parts. The first part was about students' perceptions of Grammarly feedback and teacher feedback. The second part was about the analysis of student essays from Grammarly feedback and teacher feedback. Furthermore, the interview was conducted using the student's first language to ensure clarity and avoid ambiguity. After obtaining the data, the researcher used data analysis from Renz et al., (2018) which included data preparation, reading the transcript, adding code to the transcript, using the team theme, creating a coding structure, giving the code, summarizing the coded data, and checking and explaining the results. The results of the data show that Grammarly and teacher feedback are well received by students. They received information about two aspects of argumentative writing using Grammarly feedback; practicality and the use of features to improve their writing. Nonetheless, Grammarly feedback does not provide thorough feedback on the substance, organization, and general quality of an argumentative essay. Furthermore, the teacher feedback that is often given is direct feedback using several symbols, such as underlining, circling, and immediately crossing out words with true or false marks around them. Since they got positive responses for both feedbacks, the researcher suggests that students use both feedbacks from Grammarly and teacher’s during the writing process. Future research is suggested to use different research methods such as experimental research to find out a significant comparison between the use of Grammarly feedback and teacher feedback in writing. Key words: Students’ Perception, Grammarly Feedback, Teacher’s Feedback, Argumentative Essays