Gummy stem blight (GSB), caused by Didymella bryoniae (Auersw.) Rehm., is a severe disease affecting Cucurbitaceae crops including melons. The resistance of current melon varieties that carry a single Gsb resistance gene is insufficient to protect against the abundant variation of the D. bryoniae isolates. Pyramiding multiple Gsb resistance genes into melon cultivars is an effective way to develop a broad resistance spectrum and to increase the duration of GSB resistance. In this study, two resistance genes (Gsb-4 and Gsb-6) from two resistant accessions, PI482398 and PI420145, were pyramided into one variety using marker-assisted selection (MAS). The donor parent 4598 that contained Gsb-4 and Gsb-6 was hybridized with muskmelon Baipicui to produce BC₁F₁ and BC₂F₁. Phenotyping and MAS enabled identification and pyramiding of two Gsb genes in individuals of F_1, BC₁F₁ and BC₂F₁. Field cultivation showed that individuals carrying both Gsb-4 and Gsb-6 had improved resistance to GSB and improved fruit quality. The results indicated that MAS-based pyramiding is an effective strategy for breeding melon cultivars with increased resistance to GSB.