Transradial access (TRA) has received considerable attention in the field of neurointervention owing to its advantages over transfemoral access. However, the difficulty of left internal carotid artery (ICA) navigation under certain anatomical conditions of the aortic arch and its branches is a limitation of right TRA. In this study the authors aimed to investigate the anatomical predictors that impede navigation of the left ICA in right TRA. From January to October 2020, 640 patients underwent transradial angiography at a single institute. Among them, 263 consecutive patients who were evaluated by contrast-enhanced MRA before transradial angiography were included in the study and assigned to success or failure groups according to whether left ICA navigation was possible or not. Several anatomical predictors were investigated to evaluate the correlation of the success of left ICA navigation in right TRA. A higher grade of the aortic arch type (type I vs type III: OR 6.323, p = 0.0171), higher height of the right subclavian artery (OR 1.071, p = 0.0068), narrower turnoff angle of the left common carotid artery (CCA) (OR 0.953, p = 0.0017), wider distance between the innominate artery and the left CCA (OR 1.784, p < 0.0001), steeper angulation of the right subclavian artery (tortuous vs kinking: OR 6.323, p = 0.0066), and steeper angulation of the left CCA (normal vs tortuous: OR 7.453, p = 0.0087; normal vs kinking: OR 51.65, p < 0.0001) were significantly associated with successful navigation of the left ICA. The cutoff value of the height of the right subclavian artery, distance between the innominate artery and the left CCA, turnoff angle of the left CCA, and diameter of the left CCA were 54.83 mm, 4.25 mm, 17°, and 6.05 mm, respectively. Successful left ICA navigation in right TRA was related to the specific vascular geometry of the aortic arch and its branches. Preprocedural evaluation of the anatomical predictors identified in this study may enhance the success rate of left ICA navigation in right TRA.