OBJECTIVE: To explore the effects of craniocervical atherosclerotic stenosis (AS) on the occurrence of neurologic deterioration (ND) in patients with small vessel occlusion (SVO) stroke and the outcomes of patients with SVO stroke with ND (SVO-ND). METHODS: Patients with SVO stroke were consecutively enrolled. AS was defined as a craniocervical artery with ≥ 50% stenosis caused by atherosclerosis. RESULTS: The presence of craniocervical AS (adjusted odds ratio [aOR] = 2.57, 95% confidence interval [CI] = 1.12-5.89, p = 0.026) and the number of craniocervical AS (aOR = 2.08, 95% CI = 1.25-3.44, p = 0.005) were associated with the occurrence of ND in patients with SVO stroke. Compared with SVO stroke patients with no craniocervical AS, the risk of ND increased in those with multiple AS (aOR = 6.47, 95% CI = 1.73-24.05, p = 0.005). The risk of poor outcomes increased in SVO-ND patients with multiple AS than SVO-ND patients with no AS (aOR = 47.75, 95% CI = 1.66-375.17, p = 0.024). CONCLUSION: The presence and the number of craniocervical AS are associated with ND in SVO stroke patients and with poststroke disability in SVO-ND patients.