The purpose of this research was to find out the effectiveness of guessing game in teaching vocabulary. The treatment was conducted on Januari 2020 at MI. Miftahul Huda Dongos. This method used experimental research. This experimental research involved experimental class and control class. The population of this research was 74 students of the fifth grade of MI. Miftahul Huda Dongos which each class consisted 38 students . The sample were class 5 A as the experimental group class and 5 B class as control group class.The test was used in collecting data : pre-test and post-test. Test consist of multiple choices items. Statistical calculation for experimental group class gave the average score of pre-test 66,71 and the average of post-test 86,71. Meanwhile, the average score of pre-test 64,74 and the average score of post-test 70,13 in control group class.Furthermore, the data was analyzed by using t-test. Based on the computation, t-test result 11,773 and t-table was 1,665. It means that t-test result was higher than t-table. It could be concluded that guessing game was effective in teaching vocabulary for fifth grade of MI. Miftahul Huda Dongos. Based on the result, it is recommended that teachers pay attention to the students about how to learn English well. It is also important to apply games especially guessing game in term of motivating students to learn English.