Radiotherapy is the treatment of choice for inoperable or incompletely excised brain tumours. A linear accelerator was installed at the University of Veterinary Medicine Vienna in 2006. The aim of this study was to analyse the first patient cohort (n=35) treated with fractionated radiotherapy at this institution. Clinical records were searched for the following inclusion criteria: focal brain lesions identified by advanced diagnostic imaging (CT, MRI) consistent with neoplastic disease and treatment with daily 3D conformal radiotherapy from a linear accelerator source. Patients receiving cyto-reductive surgery prior to radiotherapy were included. Seizures were the most common presenting sign. The median total radiation dose was 48 Gray. The median overall survival time was 590 days, with 1-year, 2-year and 3-year estimated survivals of 71%, 46% and 26%, respectively. Dogs that were treated at an age older than ten years had significantly longer survival times (1,093 days) than younger dogs (502 days). Weight, presentation with seizures, vision deficits, ataxia or PU/PD and anatomical location did not have an impact on survival. Overall, 3D conformal radiotherapy represents an efficient and safe treatment for brain tumours in dogs and is associated with a survival benefit.