The study aimed to examine the effect of using inquiry-based learning on enhancing 4th primary stage students' 21st century EFL literacy. The study begins with a review of the literature and previous studies about inquiry-based learning and 21st century EFL literacy. The researcher prepared a list of specifications of the 21st century EFL literacy components and performance indicators to guide the researcher to design study instruments. The researcher also designed a pre/post 21st century EFL literacy test and a rubric. The researcher developed the proposed program. Then, she nominated a random group of participants n=30 4th primary stage students at Manaret Heliopolis International School, Nasr City, Cairo, Egypt to participate in the study and its activities. Their ages ranged between 9 and 10 years old. The participants were submitted to a pre and post-test, and results were analyzed using the T-test and the effect size factor. Then, the scores were analyzed qualitatively and quantitatively, describing students' performance while conducting the study program and the pre/post-test. The results showed that inquiry-based learning effectively enhanced 4th primary stage students' 21st century EFL literacy.