This research aimed to measure whether students’ speaking ability improved by using Inside-Outside Circle (IOC) model and to know the aspects of speaking that receive more improvement. The sample of this research was students grade X of Darul Ihsan Islamic Senior High School at academic year 2021/2022. The quasi-experimental research used in this research which divided into two groups, experimental and control group. Each group consisted of 30 students, with 60 students in total. In collecting the data, I used oral pre-test and post-test. The Experimental group used Inside-Outside Circle (IOC) method in learning activity, while discussion and lecturing method used by the control group. Based on the test, the pre-test experimental group mean score was 63.83 and the post-test experimental group mean score was 86.9. Meanwhile, the pre-test control group mean score was 62.3 and the post-test control group mean score was 66.2. Thus, the T-test result in this research was 22.67 and the T-table was 2.00 at significant level 0.05 with df = n – 1 = 60 – 1. The alternative hypothesis (Ha) was accepted and the null hypothesis (Ho) was rejected. In addition, the most significant aspect of speaking was fluency that increased from 113 points to 168. This result indicates that there was significant effect on students’ speaking skills by using the Inside-Outside Circle (IOC) model.