To examine the causality between hypertension, diabetes, other cardiovascular risk factors, lifestyle behaviors, and the aortic aneurysm among patients of European ancestry. We performed two-sample Mendelian randomization (MR) analysis to investigate the causality of 12 modifiable risk factors with aortic aneurysm, including hypertension, body mass index (BMI), waist-hip ratio (WHR), diabetes, tobacco smoking, alcohol and coffee consumption, physical activity, and sleep duration. Genome-wide significant genetic instruments ( < 5 × 10) for risk factors were extracted from European-descent genome-wide association studies, whereas aortic aneurysm genetic instruments were selected from the UK Biobank and FinnGen cohort. The inverse-variance weighted MR was used as the main analysis, and MR-Egger (MRE), weighted median MR, MR pleiotropy residual sum and outlier, and Phenoscanner searching were performed as sensitivity analyses. Furthermore, we calculated MRE intercept to detect pleiotropy and Cochran's Q statistics to assess heterogeneity and conducted bidirectional MR and MR Steiger tests to exclude the possibility of reverse causality. We observed significantly higher risks for the aortic aneurysm in hypertension [pooled OR: 4.30 (95% CI 2.84-6.52)], BMI [OR: 1.58 (95% CI 1.37-1.81)], WHR [OR: 1.51 (95% CI 1.21-1.88)], WHR adjusted for BMI (WHRadjBMI) [OR: 1.35 (95% CI 1.12-1.63)], age of smoking initiation [OR: 1.63 (95% CI 1.18-2.26)], and tobacco use (initiation, cessation, and heaviness) [OR: 2.88 (95% CI 1.85-2.26)]. In sensitivity analysis, the causal effects of hypertension, BMI, WHRadjBMI, and tobacco use (initiation, cessation, and heaviness) remained robust. There was a positive causal relationship between hypertension, BMI, WHR, and WHRadjBMI and aortic aneurysm.