The aim of the study was to improve preparatory stage pupils' communicative grammar performance using task-based language instruction. The study problem was the low scores of the first year preparatory stage pupils' communicative grammar performance obtained from the pre-research. The participants of this study consisted of (N=60). Pupils enrolled at the first year preparatory stage at Kafr-Saqr Preparatory School for Girls, Sharkia Governorate, Egypt, in the academic year (2018-2019). They were randomly divided into two groups: Experimental group (N=30), and control group (N=30), during the treatment period, first-group participants received task-based language instruction, while second-group participants received instruction through traditional method. Firstly, pupils were administered a pre-test, then a post-test was administered to evaluate whether the progress between pre and post-test results were meaningful or not. The analyzed results clearly demonstrated the significance contribution of Task-Based Language Instruction to the EFL first year preparatory stage pupils' communicative grammar performance. Hopefully, these findings would be beneficial to those studying and teaching English to L2 learners.