Abstract Vision loss occurs in children with brain tumour due to prolonged pre-diagnostic raised intra-cranial pressure or by direct involvement of visual pathway structures. The HeadSmart campaign was launched in 2011 to disseminate national referral guidelines for brain tumor diagnosis, published in 2008 and demonstrated to be associated with a reduction in Total Diagnostic Interval (TDI) from 13.4 weeks in 2006 to 6.7 weeks in 2014. Records of patients with brain tumor diagnosed aged 0–24 years from the National Cancer Registry (1997–2012, n = 19,555) were probabilistically linked to 13,013 national records of the electronic Certificate of Visual Impairment (eCVI, 2007–2012), to identify 336 brain tumor patients with registered partial or complete vision loss. Variation in the risk of vision loss associated with different tumor location and histology was estimated. In this cohort CNS neoplasm, optic atrophy and multiple causes accounted for 36%, 17.5% and 15.3%, respectively, of eCVI certifications. Overall, vision loss occurred in 3.7% of childhood brain tumor patients up to two years after diagnosis. The risk was greatest (6.0%) in 0–5 year-olds and lowest (1.5%) in 19–25 year-olds. Tumours above the tentorium (5.1%), cranial nerve (4.5%) and in the midline (4.2%) pose the highest risk. Pilocytic astrocytomas, choroid plexus tumors, sellar tumors, nerve sheath tumors and pineal tumors were also strongly associated with vision loss. eCVI registrations fell from 5.8% in 2007 to 3.5% in 2011. Brain tumour was the commonest cause of blindness certification, affecting 6% of children aged <5 years, it was most common in benign / slow growing tumors affecting midline structures. The proportion with blindness certification has fallen between 2007–2012, coinciding with the reduction in reported TDI since the launch of referral guideline, which was the focus of the subsequent HeadSmart campaign. Certifications data provided by the Certifications Office (The Royal College of Ophthalmologists, c/o Certifications Office, Moorfields Eye Hospital), captured by the Certificate of Vision impairment (CVI) are Department of Health copyright and this work was made possible by collaboration with the Royal College of Ophthalmologists. Any views expressed in the publication are those of the author(s) alone and not necessarily those of the Department of Health.