This study wanted to see method do Non-English Department Students used to improve their vocabulary mastery. There were three research questions of this study “What methods do Non-English Department Students use to improve their vocabulary?”, “What problems do Non-English Department Students face in improving their vocabulary mastery?”, “What solutions do Non-English Department Students take to solve those problems?”. This research adopted a qualitative approach that took a place at non-English education department UMY and took four student as the participants of this study which were two students from Accounting Department batch 2014 and two students from Communication department batch 2014. Based on data collection, this study resulted various findings about methods used by non-English department to improve vocabulary mastery; watching movie, listening to song or music, reading book, and playing role-playing game (RPG). Meanwhile, the problems they faced to improve their vocabulary mastery; low English proficiency and personal problem. Moreover, in solutions they took to solve those problems; ask other people, translate, confident to try and always practice, mark the word and make a note. In conclusion, this study can state that there are various methods do non-English department students to improve their vocabulary mastery, and in every methods, there are problems faced by them, non-English department students also had solutions to solve their problem.