English vocabulary is fundamental learning materials for students to learn English skills. Vocabulary is content of language. It is used to develop sentences or statements for written and spoken language. However, in senior high school 7 Pinrang, South Sulawesi, many students get difficulties in mastering English vocabulary. This study aims to describe students’ problems in mastering English vocabulary. This study used descriptive quantitative method. Questionnaire was used to collect data from 133 students. Questionnaire consists of 20 item numbers of statement. It includes problems of word meaning, pronunciation and spelling, word formation, motivation, facilities, teaching method. Data was analyzed by using descriptive statistics that include mean score, frequency, and percentage and Likert scale. Category of students’ problems was divided into very high (81%-100%), high (61%-80%), medium (41%-60%), low (21%-40%), and very low (0%-20%). The findings showed that students’ problem in mastering vocabulary was categorized into high (69%). The detail problems in mastering English vocabulary were students’ problems relate to (1) word meaning was high (78%), (2) pronunciation and spelling was high (72%), (3) word formation was high (75%), (4) motivation was high (68%), (5) facilities was high (61%), and (6) teaching method was high (62%). It can be concluded that students have high problems in mastering vocabulary and students get more problems in mastering English vocabulary relates to materials of vocabulary learning than to motivation, facilities, and method.