Abstrak
The purpose of the research was to determine the effect of using the guessing game on the students' vocabularies achievement at seventh-graders in class VII B of SMP Muhammadiyah 2 Tarakan. The research design was a one group pretest-posttest design. The research was conducted at seventh-grade students in class VII B of SMP Muhammadiyah 2 Tarakan, with a total of 22 students. The research data were collected using a written test. The data were analyzed using SPSS 23 software. The results of the research showed that there was a significant increase in student scores of 15.68%, with an average pre-test score of 36.82 and a post-test score of 52.50. Based on data analysis, the alternative hypothesis (Ha) was accepted. This means that the use of the guessing game had a significant effect on the students' vocabularies achievement at seventh-graders in class VII B of SMP Muhammadiyah 2 Tarakan.