This research aims to know students’ motivation in learning English and to know vocabulary mastery at English Education Department of Universitas Muhammadiyah Yogyakarta (EED UMY) and to find out the relationship between students’ English learning motivation and their vocabulary mastery. This research was conducted in English Education Department of Universitas Muhammadiyah Yogyakarta. The population of English Education Department of Universitas Muhammadiyah Yogyakarta batch 2013 was 166 students. The participant in this research was 97 students of English Education Department of Universitas Muhammadiyah Yogyakarta batch 2013. This research used quantitative approach and correlation methodology. This research used two instruments namely questionnaire to find out students learning motivation and vocabulary test to find out students vocabulary mastery. The research found that students’ at English Education Department of Universitas Muhammadiyah Yogyakarta batch 2013 had high motivation. It was supported by the motivation with mean value was 96,38. The research also found out that vocabulary mastery was low category with mean value 23,42. The last result showed that the relationship between students’ English learning motivation and vocabulary mastery was low criteria of correlation. The correlation was a positive correlation with the correlation value was 0,209 and probability value 0,040 meaning there was a significant correlation between students’ English learning motivation and vocabulary mastery of Englsih xi Education Department of Universitas Muhammadiyah Yogyakarta batch 2013. Therefore, the hypothesis of Ha that was accepted because there was a significant positive relationship between students’ English learning motivation and their vocabulary mastery and the hypothesis of H0 was rejected.