Tan spot is a foliar disease caused by the fungus Pyreniphora tritici-repentis affecting durum wheat cultivation and production worldwide. Developing tan spot resistant varieties is an environmentally friendly way to control the disease. In this study, I introgressed the favorable allele of a race non-specific QTL mapped on chromosome 3B (TS-3B-QTLrn) into two durum wheat cultivars “Grano” and “Riveland” via marker-assisted backcross selection. I found that the introgression lines with the favorable allele had significantly lower disease severity than the recurrent parents “Grano” and “Riveland” for all four isolates tested. Phenotyping of the BC4F2 progenies indicated that the TS-3B-QTLrn showed partially dominant resistance. Further research will be conducted to test the effectiveness of the TS-3B-QTLrn on disease severity of adult plants under field conditions, as well as to test if the introgression of the TS-3B-QTLrn has effects on grain yield and quality related traits.