The design of this research was descriptive qualitative research in nature. It concerned on the strategies used by the teacher and how the strategies were applied to assist students’ vocabulary mastery in reading skill. The research was conducted at class VII MTsN Model Banda Aceh, specifically in reading skill. The researcher collected the data through interview guide, observation checklist and document analysis as the instruments. The data sources were gathered from an English teacher of MTsN Model Banda Aceh. The data were presented in the forms of list and narration. The result showed that the teacher used vocabulary journal as the strategy and applied the strategy systemically to assist students’ vocabulary mastery in reading skill. Even though the strategy takes time to introduce unfamiliar words found in the text, the rate of students’ success to comprehend the reading content is high.