The objectives of the research are to find out (1) how the teachers plan online learning in Indonesian language, (2) how the teachers implement online learning of Indonesian language, and how the teachers assess students’ achievement in Indonesian language for senior high school students at Gorontalo City. The research used qualitative approach with case study. The informant were teacher and students. Data were collected by using observation, interview, and documents, and data were analyzed qualitatively. The research findings indicated that (1) teachers have done planning for online learning of Indonesian language according to syllabus and lesson plan of Indonesian language at students of senior high schools, (2) the teachers used online learning application when they taught Indonesian language, and (3) the teachers gave assessment to students in order to evaluate the students’ learning achievement of Indonesian language. Therefore, online learning of Indonesian language has been done by teachers by applying zoom cloud meeting, google classroom, google form, and WhatsApp for communication.