Polysulfated glycosaminoglycans (PSGAGs) have been used for decades in a variety of species for the management of osteoarthritic pain. However, reports on the use of PSGAGs in avian species are scarce. In domestic cats and dogs, PSGAG injections have caused prolongation of clotting times but are considered to be an efficacious drug with a wide margin of safety. This publication documents four cases of fatal coagulopathies in different avian species (one coraciiforme, two raptors, and one psittacine) following the intramuscular administration of PSGAG. All affected birds received varying dosages and dosing intervals of PSGAG. Three of the four birds experienced fatal hemorrhage into the pectoral muscle, while the fourth bled continuously from the injection site. Only one bird had chronic, severe pre-existing disease; the remainder were being managed for osteoarthritis. This report highlights the importance of species-specific dosing of PSGAG and warrants further investigation into the etiopathogenesis of this process.