Studies have reported the importance of intervention programs to support early literacy in preschool. However, very few studies have tested the efficacy of intervention programs based on the syllabic method. This study aims to evaluate the effectiveness of a novel computer-based program based on the syllabic method for preschoolers (the Simo-syl program). Sixty-three 5-year-old children participated in the study, and their language and early literacy skills were tested. Thirty-four of them were included in the 12-week computer-based intervention program. The early literacy skills of all the children were then re-tested. The Simo-syl group showed a significant improvement in the syllabic segmentation and word identification tasks. Children with low language competences displayed greater improvements after the intervention than children with higher language competences. The Simo-syl intervention program effectively promotes early literacy skills, especially for children with language fragilities.