Background: Low circulating homoarginine as well as high levels of asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) have been associated with impaired cardiovascular (CV) outcome and mortality in patients at risk and in the general population. The present study aimed to formulate reference intervals for serum homoarginine, ADMA, and SDMA to improve risk stratification between healthy individuals and individuals at risk. Methods: We determined age- and sex-specific reference intervals for homoarginine, ADMA, and SDMA in a subgroup of 1359 healthy participants (no diabetes mellitus, CV disease, increased blood pressure, elevated blood lipids, chronic kidney disease stadium III or IV, or a body mass index >30) of the Study of Health in Pomerania (SHIP) using quantile regression analyses. Homoarginine, ADMA, and SDMA serum concentrations were measured using liquid chromatography-tandem mass spectrometry. Results: Median age of the investigated cohort was 36 (25th; 75th percentile 28; 47) years, with 62% women. Median serum concentrations of homoarginine, ADMA, and SDMA were 2.63 (2.08; 3.32) μmol/L, 0.64 (0.57; 0.73) μmol/L, and 0.43 (0.37; 0.49) μmol/L, respectively. Serum levels of homoarginine, ADMA, and SDMA showed material age- and sex-related differences (p<0.05 for all). Overall reference ranges were 1.41–5.00 and 1.20–5.53 μmol/L (2.5th; 97.5th percentile; for men and women, respectively) for homoarginine, 0.41–0.95 and 0.43–0.96 μmol/L for ADMA, and 0.30–0.67 and 0.27–0.63 μmol/L for SDMA. Conclusions: We formulated for the first time homoarginine, ADMA, and SDMA reference intervals in serum. These reference intervals might be useful for individual CV risk stratification.