Objectives -Describe unexpected events (UEs) that occurred during blood donation in cats with and without sedation.Design -Retrospective observational study (2010 -2013).Setting -University teaching hospital.Animals -Client-owned healthy cats enrolled in a blood donation program.Interventions -None.Measurements and Main Results -Blood collection for transfusion was performed 115 times from 32 cats. Seventy donation events were in unsedated cats and 45 in sedated cats. For each collection, the anticipated blood volume to be collected, actual blood volume collected, sedation protocol, and any UEs in the peri-donation period were recorded. There were 6 categories of UEs: movement during donation, donor anxiety, inadequate collected blood volume, jugular vessel-related UEs, additional sedation requirement, and cardiorespiratory distress. Fisher's exact test was used to compare the frequency of UEs between sedated and unsedated cats. Unexpected events were recorded in 54 of 115 collections. In the donor population, movement was reported as an UE in 0 cats that donated under sedation and 24/70 (34.3%) cats that donated without sedation (P<0.001). Donor anxiety occurred in 2/45 (4.4%) cats that donated under sedation and 14/70 (20.0%) cats that donated unsedated (P=0.014). Unsedated donation did not increase the likelihood of inadequate donation volume, jugular vessel-related UEs, or cardiorespiratory distress. Eight of 45 (17.8%) sedated donations required additional sedation.Conclusions -Movement during donation and signs of donor anxiety were more frequent in unsedated cats. These were considered minor issues, expected in unsedated cats being gently restrained. Blood collection from unsedated feline donors is a viable alternative to sedated donation. Abbreviations UE -unexpected event