Objective Traditional epidemiological studies have shown that C-reactive protein (CRP) is associated with the risk of cardiovascular diseases (CVDs). However, whether this association is causal remains unclear. Therefore, Mendelian randomization (MR) was used to explore the causal relationship of CRP with cardiovascular outcomes including ischemic stroke, atrial fibrillation, arrhythmia and congestive heart failure. Methods We performed two-sample MR by using summary-level data obtained from Japanese Encyclopedia of Genetic association by Riken (JENGER), and we selected four single-nucleotide polymorphisms associated with CRP level as instrumental variables. MR estimates were calculated with the inverse-variance weighted (IVW), penalized weighted median and weighted median. MR-Egger regression was used to explore pleiotropy. Results No significant causal association of genetically determined CRP level with ischemic stroke, atrial fibrillation or arrhythmia was found with all four MR methods (all Ps > 0.05). The IVW method indicated suggestive evidence of a causal association between CRP and congestive heart failure (OR:1.337, 95％ CI: 1.005–1.780, P = 0.046), whereas the other three methods did not. No clear pleiotropy or heterogeneity were observed. Conclusions Suggestive evidence was found only in analysis of congestive heart failure; therefore, further studies are necessary. Furthermore, no causal association was found between CRP and the other three cardiovascular outcomes.