Risk factors and biomarkers show promise for identifying high risk calves entering rearing facilities. Rapid automated leukocyte differential cell counts may be a good addition to augment or refine calf risk identification protocols. The objective of this study was to validate an automated leukocyte cell counter, the QScout BLD test (Advanced Animal Diagnostic, Morrisville, NC), in its ability to determine leukocyte differential cell counts in neonatal Holstein calves. From June to July 2018, blood samples collected in EDTA anticoagulant from 235 calves upon arrival at a veal research facility in Ontario, Canada, were evaluated by both the QScout BLD test and by manual leukocyte differential counts done by microscopy. These tests were compared using Lin’s concordance correlation coefficient (−1 (perfect discordance) < ρ < 1 (perfect concordance)) and revealed very good agreement between tests for neutrophil counts ρ = 0.83 (P < 0.001); fair agreement for lymphocyte counts ρ = 0.32 (P < 0.001); slight agreement for monocyte counts ρ = 0.14 (P < 0.001); and, slight agreement for eosinophil counts ρ = 0.20 (P < 0.026). Test results were further examined to determine if they differed in their classification of samples as being above, within, or below reported 95% reference intervals for neonatal Holstein calves. Classification between tests resulted in very good agreement with only 4.2% and 5.8% disagreement in classification for neutrophils and lymphocytes, respectively. Moderate agreement for monocytes was observed with 23.3% classified differently; and, poor agreement was observed for eosinophils with 70.3% classified differently. Further study is required to determine the role of the leukocyte profile in risk assessment of neonatal calves. However, rapid leukocyte differentials that can be measured on farm present a promising addition for potential use in selective antimicrobial therapy protocols with the purpose of reducing antimicrobial use in veal and dairy beef facilities at arrival.