Aims: This study aims to investigate the association between serum small dense low-density lipoprotein (sdLDL) cholesterol level and the development of coronary heart disease (CHD) in a Japanese community. Methods: A total of 3,080 participants without prior cardiovascular disease, aged 40 years or older, were followed up for 8 years. The participants were divided into the quartiles of serum sdLDL cholesterol levels. The risk estimates were computed using a Cox proportional hazards model. Results: During the follow-up period, 79 subjects developed CHD. Subjects in the highest quartile had a 5.41- fold (95% confidence interval, 2.12–13.82) higher risk of CHD than those in the lowest quartile after controlling for confounders. In the analysis classifying the participants into four groups according to the levels of serum sdLDL cholesterol and serum low-density lipoprotein (LDL) cholesterol levels, the risk of CHD almost doubled in subjects with sdLDL cholesterol of ≥ 32.9 mg/dL (median), regardless of serum LDL cholesterol levels, as compared with subjects with serum sdLDL cholesterol of ＜32.9 mg/dL and serum LDL cholesterol of ＜120.1 mg/dL (median). When serum sdLDL cholesterol levels were incorporated into a model with known cardiovascular risk factors, c-statistics was significantly increased (from 0.77 to 0.79; p=0.02), and the net reclassification improvement was also significant (0.40; p＜0.001). Conclusions: The present findings suggest that the serum sdLDL cholesterol level is a relevant biomarker for the future development of CHD that offers benefit beyond the serum LDL cholesterol level and a possible therapeutic target to reduce the burden of CHD in a Japanese community.