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Salt and drought stresses are major environmental pressures in agriculture worldwide and affect crop productivity and quality. The previous reports of the R2R3‐MYB transcription factor (TF) genes found that overexpression of these TF genes regulated the expression of key enzyme‐encoding genes of flavonoid biosynthesis pathway, leading to the increased flavonoid accumulation. However, the roles of the cotton (Gossypium hirsutumL.) R2R3‐MYB transcription factor gene GhMYB4in regulating flavonoid accumulation and abiotic stress tolerance have not been investigated. In this study, the GhMYB4gene was isolated from cotton. The observed subcellular localization in onion (Allium cepaL.) epidermal cells demonstrated that GhMYB4was concentrated in the nucleus. A transactivation assay showed that this gene was transcriptionally active. The increased flavonoid accumulation and enhanced salt and drought tolerance of Arabidopsisoverexpression plants were revealed. Under salt and drought stresses, proline and soluble sugar contents significantly increased, whereas H2O2and malondialdehyde contents significantly decreased in transgenic plants. Further enzymatic analysis showed significant increases of superoxide dismutase, catalase, ascorbate peroxidase, and peroxidase activities in transgenic plants. Real‐time quantitative polymerase chain reaction analysis showed that overexpression of GhMYB4up‐regulated the genes involved in flavonoid biosynthesis, proline biosynthesis, and reactive oxygen species scavenging in plants under salt and drought stresses. The overall results demonstrate that GhMYB4has the potential to promote production of growth‐benefiting flavonoids and improve tolerance to abiotic stresses in plants. The cotton GhMYB4gene improved flavonoids accumulation.GhMYB4enhanced salt and drought tolerance in transgenic Arabidopsisplants.Overexpression of GhMYB4increased the expression of genes involved in flavonoid biosynthesisGhMYB4overexpression up‐regulated the expression of genes related to abiotic stresses.