Purpose: To estimate the prevalence and causes of visual impairment (VI), among primary school children in Mekelle, Ethiopia and the feasibility of teachers conducting vision screening in school using a smart phone application:Peek Acuity. Methods: The study was conducted in four schools in Mekelle among children in their final 2 years of primary school (ages 11–15 years). Six teachers were trained in Peek Acuity, inter-observer variation was assessed and all teachers attained acceptable agreement (kappa>0.7) after one or two training sessions. Trained teachers then screened all eligible children for vision impairment in each eye using Peek Acuity. Children with visual acuity less than Log MAR 0.3 in either eye were examined by optometrists to determine the causes of VI. Results: 1137 out of 1197 children participated (95.1%) with a mean age of 13 years. 141 children (12.4, 95% CI 10.5–14.3) had VI (presenting VA<0.3) in either one or both eyes. The prevalence of presenting VA<0.3 in the better eye was 6.7% (95% CI: 5.2–8.1) and the prevalence of unilateral VI (presenting VA<0.3 in one eye) was 5.7 % (95% CI: 4.4–7.2). Uncorrected Refractive Error was the leading cause of VI (89%). No children had previously worn spectacles. Conclusion: High levels of unmet need for eye examination and spectacle provision were found. School-based screening using Peek Acuity was an effective means to identify and refer children who could benefit from spectacle correction and other treatment to restore vision.