Good writing skills are vital to success in school and, later, in the workplace. However, many elementary and secondary students fail to invest sufficient time and effort in planning what they want to write and, consequently, produce texts of inferior quality. One approach to help struggling children and adolescents acquire effective writing planning abilities is called story-mapping. In this single-case study, the story-mapping method was applied in a peer-tutorial setting to help three low-achieving fifth graders brainstorm their ideas and organize their thoughts prior to composing a narrative. During the course of the intervention, all tutees were able to significantly increase the number of words that they generated to write their texts. The study demonstrated that peer-tutoring can be successfully implemented to combat deficiencies in writing planning skills and help struggling students to improve their performance in a meaningful way.