Background: The comparative effectiveness of radiotherapy and surgery for treating intracranial meningioma is unknown. Objectives: To compare survival after treatment of suspected intracranial meningioma by either surgery or radiotherapy. Animals: Two hundred eighty-five companion dogs with suspected intracranial meningiomas presenting to 11 specialty clinics in three countries. Methods: Parallel cohort comparison study on retrospective data. Dogs diagnosed with intracranial meningioma by board-certified veterinary neurologists or radiologists and treated by radiotherapy or surgery were identified through medical record searches and presenting and survival data extracted. Lesion site was classified as rostro- or caudotentorial and size was measured on contrast magnetic resonance images. Outcome was all-cause death. Analysis of survival by Cox proportional hazards, including selection for optimal multivariable model using lasso, counterfactual modeling including variables associated with treatment allocation and survival. Results: One hundred sixty-eight dogs received radiotherapy and 117 received surgery. All analyses indicated reduced survival associated with surgery compared to radiotherapy. There was a median survival after surgery of 297 (IQR: 99–768) days compared with 696 (IQR: 368–999) for dogs treated by radiation, associated with a univariable hazard ratio of 1.802 (95% CI: 1.357–2.394). Counterfactual modeling estimated a mean survival of 480 (95% CI: 395–564) days after surgery and 673 (95% CI: 565–782) days after radiotherapy, representing a decrease in survival of 29%. Location and size of the lesion were not associated with survival duration. Conclusions and Clinical Importance: Dogs with suspected intracranial meningioma have substantially superior survival after radiotherapy compared to surgery.