Writing becomes increasingly more imperative across all content areas as students progress through secondary school. However, many of them struggle with the complex process of putting thoughts and ideas onto paper or into a keyboard. Adolescents with learning disabilities (LDs), in particular, are usually challenged by writing activities. One major cause for their difficulties is their lack of planning skills. This single-case study evaluated a peer-tutoring approach designed to teach adolescents with LDs to better plan narratives by using a simple strategy (story mapping). A multiple-baseline design (AB) across subjects was employed to assess the effects of the intervention. The results indicate large and significant effects of the intervention on the length and completeness of the narratives the students produced. This suggests that writing skills of adolescents with LDs can be improved by way of peer tutoring with limited resources required.