Vegetable soybean (Glycine max L.) is an important economic and nutritious crop in South and Southeast Asian countries and is increasingly grown in the Western Hemisphere. Aromatic vegetable soybean is a special group of soybean varieties that produce young pods containing a sweet aroma, which is produced mainly by the volatile compound 2-acetyl-1-pyrroline (2AP). Due to the aroma, the aromatic vegetable soybean commands higher market prices and gains wider acceptance from unfamiliar consumers. We have previously reported that the GmAMADH2 gene encodes an AMADH that regulates aroma (2AP) biosynthesis in soybeans (Arikit et al. 2010). A sequence variation involving a 2-bp deletion in exon 10 was found in this gene in all investigated aromatic varieties. In this study, a codominant PCR-based marker for the aroma trait in soybeans was designed based on the 2-bp deletion in GmAMADH2. The marker was verified in five aromatic and five non-aromatic varieties as well as in F(2) soybean population segregating for aroma. The aromatic genotype with the 2-bp deletion was completely associated with the five aromatic soybean varieties as well as the aromatic progeny of the F(2) population with seeds containing 2AP. Similarly, the non-aromatic genotype was associated with the five non-aromatic varieties and non-aromatic progeny. The perfect co-segregation of the marker genotypes and aroma phenotypes confirmed that the marker could be efficiently used for molecular breeding of soybeans for aroma.