The aim of this study was to develop a science experimental guidebook for the mainstreamed students with learning disabilities and investigate its effect on their conceptual understanding of physical events. Through case study research methodology, the sample of the study consisted of 12 mainstreamed students with learning disabilities. To collect data, a conceptual understanding test, a drawing test, and interviews were used. The data were analyzed using four categories (sound understanding, partial understanding, alternative understanding, and no understanding). The results showed that the guidebook positively affected conceptual understanding of the mainstreamed students with learning disabilities. Even though the mainstreamed students with learning disabilities tended to comprehend related concepts through hands-on and minds-on activities/experiences, they still had some problems at transferring their gained knowledge to novel situations. Moreover, the results indicated that the mainstreamed students with learning disabilities were more successful in expressing their thoughts with drawings than the conceptual understanding test and interviews. The present study suggests that future studies should implement interdisciplinary approaches that intertwine special education with science education, mathematics education, and reading-writing practices.