The purpose of my book is to investigate the effect of using performance-based assessment on tenth grade students' language accuracy achievement at Mafraq Directorate of Education. The researcher followed the equivalent pre/post T test two group designs. To achieve the purpose of the study, a pre/post-test comprehension test with grammar components was constructed to measure students' achievement in language accuracy. The test consisted of four components: Reading comprehension questions, grammar questions, vocabulary questions and writing questions The findings indicated that there were statistically significant differences in the post- test between the control and the experimental groups in favor of the experimental group, and there was no statistically significant difference in the students' achievement due to gender. There was no statistically significant difference due to the interaction between gender and group. The researcher proposed some recommendations to enhance the effect of using performance-based assessment on students' language accuracy such as conducting further studies on other populations and for a longer time