Background and Purpose: Intracranial atherosclerotic disease (ICAD) is a common etiology of acute vertebrobasilar artery occlusion (VBAO) in Asia, which complicated endovascular treatment (EVT). We aimed to investigate the incidence, impacts, and predictors of ICAD in VBAO. Methods: Subjects were selected from the Endovascular Treatment Key Technique and Emergency Work Flow Improvement of Acute Ischemic Stroke registry and divided into two groups based on whether underlying ICAD existed. Underlying ICAD was determined when the following situations arise in the occlusion site during EVT: (1) fixed stenosis degree >70% or (2) stenosis >50% with distal blood flow impairment or evidence of repeated reocclusion. Multivariable regression models were used to investigate the effect of underlying ICAD on outcomes measured by modified Rankin Scale (mRS) score at 90 days and to identify baseline characteristics associated with underlying ICAD. Results: Among the 315 patients enrolled, 171 (54.3%) had underlying ICAD. Favorable functional outcomes (mRS 0–3) occurred in 79 of 163 patients (48.5%) with ICAD and 69 of 137 patients (50.4%) without ICAD ( p = 0.743). Outcomes were similar between the two groups and remained similar after adjusting for the confounders. History of hypertension and elevated admission neutrophil to lymphocyte ratio were strong predictors of underlying ICAD, whereas history of atrial fibrillation and distal basilar artery occlusion were negative predictors. Conclusions: In our study, underlying ICAD was recognized in approximately half of the VBAO patients, leading to comparable outcomes after more complex EVT strategies. Some baseline characteristics were identified to be predictors for underlying ICAD, which were helpful to guide the EVT strategies before the procedure.