English has been a particular subject at schools. Most of the students have difficulties in mastering its vocabulary and grammar. Therefore, at this time the researcher conducted a research which aimed to reveal the effects of using whiteboard animation toward the student's vocabulary and grammar mastery. The researchers used the experimental research. The sample of research consisted of two groups from the eighth grade students at Indonesian Junior high school. For data collection were taken from pre-test and post-test. The results of were analysed using T-test to verify the hypothesis of the research. The results of this research indicate that whiteboard animation has positive effects on mastering English vocabulary and grammar. There was 58.9% improvement from the experimental group for the vocabulary. While for the control group, there is 37% improvement. For grammar test, the experimental group shows impressively significant difference with more than 100% improvement. While the control group shows 50.5% improvement in the grammar test. In conclusion, the researchers found that students who learn vocabulary and grammar through whiteboard animation show more significant improvement than the control group taught by conventional teaching method. The researchers also measured the effect size between vocabulary post test score with R squared of 0.321 and grammar post-test score with R squared of 0.485 from the experimental group. Based on the results of the research, the researchers concluded that whiteboard animation has significant effect towards both students' vocabulary and grammar with more improvement on grammar mastery though.