This research was aimed to investigate the effectiveness of clustering technique for teaching writing narrative text at the tenth grade of SMA Negeri 3 Purwokerto in academic year 2014/2015. This research used quasi experimental research. The participants of this research were the tenth grade students in SMA Negeri 3 Purwokerto. The two classes were chosen as the experimental class (X IPA 3) consisting of thirty two students, and control class (X IPA 4) consisting of thirty two students. The technique of data collection used test, namely; pre-test and post-test. Based on the analysis of data, the mean score of pre-test in experimental class was 65.3, and the mean score of post-test was 76.2. The mean score of control class was 63.7 and the mean score of post-test was 68.9. The improvement was 10.9 from pre-test to post-test in the experimental class and the improvement in the control class was 5.2 from pre-test to post-test. The result of t-test was 3.4969, while the t-table with the significant level 0.05 in df 62 was 1.6698. Therefore, t-test was higher than t-table or 3.4969> 1.6698, so that the hypothesis which stated that clustering technique gave positive effect for teaching writing narrative text was accepted.