BACKGROUND: Intracranial aneurysms (IAs) represent a significant and potentially fatal category of cerebrovascular disorders that pose serious health risks. Observational studies have indicated a potential link between brain imaging-derived phenotypes (IDPs) and various IAs. Nonetheless, the nature of these relationships remains ambiguous. METHODS: Two-sample bidirectional Mendelian randomization (MR) analyses were performed to examine the causal links between IDPs and IAs. We utilized summary statistics from a population comprising 587 brain IDPs (UK Biobank). Additionally, we incorporated data of IAs from the HUNT study. RESULTS: We identified a total of 13 IDPs that demonstrated a significant causal influence on the risk of developing IA, subarachnoid hemorrhage, and unruptured IA by forward MR. Specifically, an increase in mean diffusivity in the right external capsule is associated with the risk of IA (odds ratio [OR] = 1.830, 95% confidence interval [CI]: 1.134-2.553, P = 1.04 × 10 CONCLUSIONS: The findings indicate that these IDPs play a crucial role in the etiology of these IAs and highlight the importance of understanding the mechanisms through which they exert their effects.