Down syndrome is acknowledged to be the most common neurogenetic cause for intellectual disability. It is a multisystem disorder which results in multiple lifelong health problems. At present, students with Down syndrome can receive education in inclusive mainstream education settings. However, this is not without its accompanying challenges. The present study aimed to investigate the challenges that teachers face in implementing Individualised Education Plans (IEPs) for children with Down syndrome in mainstream schools in Riyadh, Saudi Arabia. A customised questionnaire was utilised to obtain the perceptions of 100 special education teachers from four mainstream schools in Riyadh. The results revealed that the teachers did not have a robust understanding of the different aspects of children with Down syndrome. They also encountered significant challenges in IEP implementation at individual or group level. In addition, the teachers indicated that there were solutions to the challenges they encountered in IEP implementation. Recommendations are discussed in the light of these findings.