Shallot basal rot caused by Fusarium oxysporum severely affects bulb quality and causes significant economic losses during postharvest storage. This study identified antagonistic soil bacteria isolated from shallot fields capable of reducing the disease under postharvest storage conditions of local farmers. The three strongest antagonistic bacterial isolates against the pathogen in dual cultures on petri plates, i.e., ATA 33, ATB 24, and ATB 32, were tested for their disease-reducing effects. Each isolate was tested using three different cell densities (10⁷, 10⁸, and 10⁹ CFU/mL) in a completely randomized experimental design. The 10⁸ CFU/mL suspension of ATB 24 significantly reduced disease incidence (53.33%) as compared to the untreated control (96.67%) after 35 days of storage. ATB 24 was identified as Streptomyces albaduncus using morphological characterization and 16S rRNA gene sequencing. Streptomyces albaduncus ATB 24 could be a biological control agent of shallot basal rot during postharvest storage in practice.