The objective of this research was to find out whether there was a correlation between students’ vocabulary mastery, grammar mastery and their reading comprehension. This study used ex post facto co-relational design. The subject of this research was class XI MIA 2 of SMAN 1 Ambarawa consisting of 32 students. The data were analyzed by using Pearson Product Moment Correlation and Multiple Linear Regression Test. The result showed that there was a statistically significant correlation between students’ vocabulary mastery, grammar mastery and their reading comprehension with the significant level 0.05. This suggests that to obtain a good reading comprehension, vocabulary mastery and grammar mastery must be improved.