Extracorporeal CO₂ removal (ECCO₂R) can permit lung protective or noninvasive ventilation strategies in patients with chronic obstructive pulmonary disease (COPD) and acute respiratory distress syndrome (ARDS). With evidence supporting ECCO₂R growing, investigating factors which affect CO₂ removal is necessary. Multiple factors are known to affect the CO₂ removal rate (vCO₂) which can complicate the interpretation of changes in vCO₂; however, the effect of hematocrit on the vCO₂ of artificial lungs has not been investigated. This in vitro study evaluates the relationship between hematocrit level and vCO₂ within an ECCO₂R device. In vitro gas transfer was measured in bovine blood in accordance with the ISO 7199 standard. Plasma and saline were used to hemodilute the blood to hematocrits between 33% and 8%. The vCO₂ significantly decreased as the blood was hemodiluted with saline and plasma by 42% and 32%, respectively, between a hematocrit of 33% and 8%. The hemodilution method did not significantly affect the vCO₂. In conclusion, the hematocrit level significantly affects vCO₂ and should be taken into account when interpreting changes in the vCO₂ of an ECCO₂R device.