Stem lignin content (SLC) in common wheat (Triticum aestivum L.) contributes to lodging resistance.  Caffeic acid 3-O-methyltransferase (COMT) is a key enzyme involved in lignin biosynthesis.  Characterization of TaCOMT genes and development of gene-specific markers could enable marker-assisted selection in wheat breeding.  In the present study, the full-length genomic DNA (gDNA) sequences of TaCOMT genes located on chromosomes 3A, 3B, and 3D were cloned by homologous cloning.  Two allelic variants, TaCOMT-3Ba and TaCOMT-3Bb, were identified and differed by a 222-bp insertion/deletion (InDel) in the 3´-untranslated region (3´-UTR).  A co-dominant gene-specific marker based on this InDel was developed and designated as TaCOMT-3BM.  A total of 157 wheat cultivars and advanced lines grown in four environments were used to validate the associations between allelic patterns and SLC.  The SLC of cultivars with TaCOMT-3Ba was significantly (P<0.01) higher than that of those with TaCOMT-3Bb, and the marker TaCOMT-3BM could be effectively used in wheat breeding.