The principal aim of this study was to document the effectiveness of tonsillectomy in dogs using a vessel-sealing device compared with a standard technique with tonsillectomy forceps. A secondary aim of the study was to document histopathological changes of the excised tonsillar tissue in dogs with brachycephalic obstructive airway syndrome. 20 dogs were studied. The time taken to remove a tonsil using LigaSure was a mean of 44.8 seconds (sd 15 seconds, 95 per cent CI 40 to 57 seconds) and with the standard technique a mean of 305.9 seconds (sd 67 seconds, 95 per cent CI 272 to 349 seconds). Significantly less haemorrhage occurred using LigaSure compared with the standard technique. Histopathology of the tonsils was characterised by multifocal neutrophilic and lymphocytic inflammation, and 1–2 mm of heat-induced coagulation necrosis at the cut edge of LigaSure tonsils. This study shows that LigaSure is significantly faster and resulted in less bleeding than the standard technique.