This study aimed at exploring the effectiveness of an electronic program based on the Accelerated Learning Theory in developing preparatory school students' EFL vocabulary use. Forty 1st year preparatory school students from Al Ghar preparatory school, Sharkia Governorate were selected and divided into two groups: an experimental group (N=20) and a control group(N=20). The experiment was conducted during the first term of the school year 2022/2023. For data collection, the following instrument was designed; a vocabulary use test and it was validated by the jury members. It was pre-post administered to both groups. Then an electronic program based on the Accelerated Learning Theory was designed and administered to the experimental group whereas the control group received regular instruction. Data obtained were analyzed using SPSS; independent samples T-test was used to compare the mean scores of the experimental and the control groups in the post administration of the study instrument. Paired Samples T-test was used to find out the difference between the mean scores of the prepost administrations of the experimental group. Results of the study indicated that the experimental group outperformed the control group in the post administration of this instrument. Findings of the current study provided evidence that the electronic program based on the Accelerated Learning Theory had a positive effectiveness in developing EFL vocabulary use of preparatory school students.