To separate posterior-circulation stroke (PCS) and vestibular-neuritis (VN) using quantitative vestibular tests. Patients were prospectively recruited from the emergency room within 72h of presentation. Video-nystagmography (VNG), three-dimensional video head-impulse testing (vHIT), vestibular-evoked myogenic potentials (VEMPs), and subjective visual-horizontal (SVH) were performed. There were 128 PCS and 134 VN patients. Common stroke-territories were: posterior-inferior cerebellar artery, basilar-perforators, multi-territory and anterior-inferior cerebellar artery (41.4%, 21.1%, 14.1%, 7.8%). VN included superior, inferior and pan-neuritis (53.3%, 4.2%, and 41.5%). Most VN and stroke patients presented with acute vestibular syndrome (96.6%, 61.7%). In VN, we recorded horizontal (98.5%) or vertical/torsional spontaneous nystagmus (1.5%) and in PCS, absent-nystagmus (53.9%), horizontal (32%) or vertical/torsional (14.1%) nystagmus. The mean slow-phase velocity of horizontal nystagmus was faster in VN than PCS (11.8 ± 7.2 and 5.2 ± 3.0°/s, p < 0.01). Ipsilesional horizontal-canal (HC) vHIT-gain was lower in VN than in stroke (0.47 ± 0.24, 0.92 ± 0.20, p < 0.001). Ipsilesional catch-up saccades occurred earlier, and their amplitude, prevalence, and velocity were greater in VN than PCS (p < 0.01). Ipsilesional SVH deviation > 2.5° occurred more often in VN than in stroke (97.6% and 24.3%, p < 0.01). Abnormal bone-conducted ocular-VEMP asymmetry ratio was more common in VN than PCS (50% and 14.4%, p < 0.01). Using the ten best discriminators (VNG, vHIT, SVH, and oVEMP metrics), VN was separated from PCS with a sensitivity of 92.9% and specificity of 89.8%. Adding VNG and vHIT to the bedside head-impulse-nystagmus-and-test-of-skew (HINTS) test enhanced sensitivity and specificity from 95.3% and 63.4% to 96.5% and 80.6%. Quantitative vestibular testing helps separate stroke from vestibular neuritis and, when used, could improve diagnostic accuracy in the emergency room.