It is not known whether combination of hypertension and high homocysteine (HHcy) impacts on stroke-related neurological severity. Our aim was to determine whether there is an interaction of hypertension and HHcy on neurological severity in first-ever ischemic stroke patients. We analyzed neurological severity among 189 consecutive first-ever ischemic stroke patients with or without hypertension or HHcy. Hypertension (odds ratio [OR]: 8.086, 95% confidence interval [CI]: 3.596–18.181, P < .001) and total homocysteine (OR: 1.403, 95% CI: 1.247–1.579, P < .001) were independently associated with neurological severity. In receiver-operating characteristic analysis, total homocysteine was a significant predictor of neurological severity (area under curve: 0.794; P < .001). A multiplicative interaction of hypertension and HHcy on more severe neurological severity was revealed by binary logistic regression (OR: 13.154, 95% CI: 5.293–32.691, P < .001). Analysis further identified a more than multiplicative interaction of hypertension and HHcy on neurological severity compared with patients without each condition (OR: 50.600, 95% CI: 14.775–173.285, P < .001). Interaction effect measured on an additive scale showed that 76.4% patients with moderate/severe neurological severity were attributed to interaction of hypertension and HHcy. Significant interaction of hypertension and HHcy on neurological severity was found on multiplicative and additive scale in first-ever Chinese ischemic stroke patients.