High-dose prednisolone is used in first-line treatment for lymphoma, but the potential adverse impact on bone health is unclear. Danish patients with diffuse large B-cell lymphoma or follicular lymphoma diagnosed between 2000 and 2012 were matched to the background population. Osteoporotic events (osteoporosis treatment or low-energy fracture) were identified using the Danish National Patient Registry and Prescription Registry. In total, 2589 patients and 12,945 controls were included. Lymphoma patients had increased risk of osteoporotic events compared to the matched population (hazard ratio 1.61 [95% confidence interval 1.40;1.84]). The 5- and 10-year cumulative risks of osteoporotic events for lymphoma patients were 10.0% [8.6;11.4] and 16.3% [13.8;18.7], whereas corresponding risks in the background population were 6.8% [6.3;7.3] and 13.5% [12.4;14.6]. Patients without osteoporotic event in the first two years after treatment were not at higher risk of osteoporotic events in subsequent years. Risk factors for osteoporotic events were female sex and age >70 years.