Children with a supratentorial midline low grade glioma (LGG) may be at risk for impaired bone health due to hypothalamic-pituitary dysfunction, obesity, exposure to multiple treatment modalities, and/or decreased mobility. The presence of impaired bone health and/or its severity in this population has been understudied. We aimed to identify the prevalence and risk factors for bone problems in children with supratentorial midline LGG. A retrospective study was performed in children with supratentorial midline (suprasellar or thalamic) LGG between 1-1-2003 and 1-1-2022, visiting the Princess Máxima Center for Pediatric Oncology. Impaired bone health was defined as presence of vertebral fractures and/or very low bone mineral density (BMD). In total, 161 children were included, with a median age at tumor diagnosis of 4.7 years (range 0.1 - 17.9) and a median follow-up of 6.1 years (range 0.1 - 19.9). Five patients (3.1 %) had vertebral fractures. In 99 patients BMD was assessed either by Dual Energy X ray Absorptiometry (n=12) or Bone Health Index (n=95); 34 patients (34.3%) had a low BMD (≤ -2.0). Impaired visual capacity was associated with bone problems in multivariable analysis (OR 6.63, 95% CI 1.83 - 24.00, p = 0.004). In this retrospective evaluation, decreased BMD was prevalent in 34.3% of children with supratentorial midline LGG. For the risk to develop bone problems visual capacity seems highly relevant. Surveillance of bone health must be an aspect for awareness in the care and follow-up of children with a supratentorial midline LGG.