Reflective writing skills is linked to lifelong learning. There are still few studies about reflective writing skills of undergraduate medical students in Indonesia, so it is necessary to investigate the reflective writing skills of undergraduate medical students. A qualitative design using content analysis method was conducted at Faculty of Medicine, Gadjah Mada University on June-August 2016. Written reflections (156) were taken from 54 third year medical students in Jogjakarta, Indonesia using random sampling technique. Every group of student encountered different problems in community as the trigger to write reflective tasks about their experiences when interacting with community. Every student has to write a reflection in three occasions, at the beginning of the program, after the first meeting with the mentor, and at the end of the program. Students’ reflective writing were analyzed by three coders using a REFLECT criteria to investigate the level of reflection. 33.3% of students at 1st level (habitual action), 48.2% reached 2nd level (thoughtful action), and 18.5% reached 3rd level (reflection). The ability of undergraduate medical student in reflective writing skills were in the range of 1st to 3rd level, of 4 levels. It is concluded that undergraduate medical students require more training in writing a critical reflection.