This study aimed at investigating the effectiveness of a successful intelligence-based program for developing English writing skills among preparatory schoolers. The participants (N=25) were divided into two groups; the experimental group and the control one. The experimental group consisted of 12 students at Al-Arish Preparatory Institute for Girls, Al-Arish city, North Sinai Governorate, whereas the control group consisted of 13 students at Al-Arish New Preparatory Institute for Girls, Al-Arish city, North Sinai Governorate. The instruments and material were prepared and validated as follows: a writing skills checklist, a writing skills pre-post test and a successful intelligence-based program. The experimental group received the successful intelligence-based program as an experimental intervention, while the control group received only the regular running program. The writing skills test was pre-administered. The successful intelligence-based program was implemented, and then the test was post-administrated at the end of the intervention. Data was collected and statistically analysed. The study results revealed that there are statistically significant differences between the mean scores of the experimental group pre and post measurements on the writing skills test in favour of the post measurement. Results also showed that there are statistically significant differences between the mean scores of the experimental and control groups on the writing skills test in favour of the experimental group. Accordingly, it is concluded that the successful intelligence-based program has a positive effect on developing the first year preparatory schoolers' writing skills.