Aberrant migration of Parelaphostrongylus tenuis in camelids results in neurologic deficits, recumbency, and sometimes death. An antemortem diagnosis of P. tenuis in camelids is typically based upon the presence of characteristic asymmetric neurologic deficits, known exposure to white-tailed deer, cerebrospinal fluid (CSF) eosinophilia, and response to treatment. The diagnostic accuracy of CSF eosinophil percentage for the diagnosis of P. tenuis in camelids has not been critically examined. The objective of the current study was to determine the sensitivity (Se) and specificity (Sp) of CSF eosinophil percentage, CSF eosinophil concentration, total nucleated cell concentration, and protein concentration for the antemortem diagnosis of P. tenuis. Medical records of camelids admitted to Cornell University with clinical signs of neurologic disease, CSF analysis, and necropsy were examined from January 2000 through December 2009. Se and Sp were determined by receiver operating characteristic curves in camelids diagnosed with P. tenuis (n = 13) or other conditions (n = 24) based on postmortem examination. More than 17% of eosinophils in CSF had a Se of 85% and Sp of 92% for P. tenuis diagnosis (area under the curve [AUC]: 0.87; SE AUC: 0.07; P < 0.0001; 95% confidence interval [CI] AUC: 0.72-0.96), and >1.4 eosinophils/µl of CSF had a Se of 85% and Sp of 96% (AUC: 0.9; SE AUC: 0.06; P < 0.0001; 95% CI AUC: 0.76-0.97). Cerebrospinal fluid eosinophil percentage and concentration are sensitive and specific methods for diagnosing P. tenuis antemortem in camelids residing in regions endemic to white-tailed deer.