The purpose of conducting this research was to prove whether the students' vocabulary mastery can be increased by using snowball throwing technique or not. This research was true-experimental research design. The population of this research was the seventh grade students of SMP Negeri 1 Ampibabo. The researcher took the students in seventh grade by using random sampling technique. The data were collected by using pre-test and post-test. The pre-test was conducted to measure the students' vocabulary mastery before treatment, while the post-test was conducted to measure the students' vocabulary after treatment. The data obtained from the test were analyzed statistically. The result of the data analysis showed that there was a significant difference between the result of experimental group and control group. It is proved that the result of t-counted (2.30) is higher than t-table (2.034). It means that the alternative hypothesis (Ha) was accepted and the null hypothesis (Ho) was rejected. Hence, the use of Snowball throwing technique can increase vocabulary mastery of the seventh grade students at SMPN 1 Ampibabo.