BackgroundLeukoreduction is a routine procedure in human transfusion medicine but is uncommon in veterinary.ObjectivesTo evaluate the effect of leukoreduction on the quality of canine whole blood (WB) and blood products during storage.AnimalsTen canine blood donors.MethodsThis is a case series study. An amount of 450 mL of blood was collected from each dog. Five WB and 5 packed red blood cells (pRBC) bags were divided into 2 units each: leukoreduced (LR) and non‐leukoreduced (nLR). RBC count, erythrocytes' mean osmotic fragility (MOF), 2,3‐diphosphoglycerate (2,3‐DPG), adenosine triphosphate (ATP), percentage of hemolysis, potassium (K), lactate, glucose, and cytokines were measured weekly from day of donation (T0) to day 35 (T35); pH, coagulation times, and clotting factors were evaluated at T0 and T35 from WB and in fresh frozen plasma after 1 year of storage.ResultsLeukoreduction showed positive effects on lactate (T35: LR WB 14.42 mmol/L SD 2.71, nLR WB 22.42 mmol/L SD 1.86, LR pRBC 20.88 mmol/L SD 2.65, nLR pRBC 36.81 mmol/L SD 2.34; P < .0001), pH (T35: LR WB 6.88 SD 0.16, nLR WB 6.69 SD 0.20, P = .02; LR pRBC 6.57 SD 0.23, nLR pRBC 6.22 SD 0.11; P < .001), and K (LR pRBC 4.08 mmol/L SD 0.88, nLR pRBC 5.48 mmol/L SD 0.90; P < .001). Increasing values of IL8 were observed in nLR units during storage (T0: 4167 ± 11 888 pg/mL; T35: 6367 ± 11 612 pg/mL).Conclusion and Clinical ImportanceLR blood units are recommended to critically ill dogs with marked inflammatory conditions.