Objective: To assess whether there was an improvement in the knowledge, attitudes and practices of students after the Healthy Eyes in Schools Project intervention and to complete a process evaluation to inform future implementation of health promotion interventions. Design: A descriptive, mixed-methods design was used, including questionnaires and interviews. Setting: Four primary schools in Aileu District, Timor-Leste. Local teachers received training and resources to implement nine lessons about eye health. The intervention was supported in two schools by the concurrent creation of school gardens and improvements to the water and sanitation, where required. Method: Students from classes 5 and 6 participated: 384 students aged 10-17 years (median = 12 years, inter-quartile range = 12-13 years) completed the baseline knowledge, attitudes and practices survey and 237 students participated in a follow-up survey. Interviews with teachers, students and parents informed the process evaluation. Results: The intervention was associated with an improvement in eye health knowledge and some attitudes and practices of students. Attitudes about the capabilities of blind children and adults did not change. The teachers' attitude and support from principals and an international non-governmental organisation appeared to be key factors in the successful implementation of the Healthy Eyes in Schools Project. The limited eye health in the existing curriculum, limited parent participation and access to healthy food may have influenced the effectiveness of the Healthy Eyes in Schools Project intervention. Conclusion: A number of benefits appeared to be associated with the inclusion of eye health topics in school health and hygiene education in Timor-Leste. Concurrent development of a supportive environment appeared to enable this initiative. The results of this evaluation can be used to advocate to the Ministries of Education and Health and other education stakeholders for the inclusion of eye health in the health and hygiene curriculum.