A well-conserved LAMMER kinase in yeast and filamentous fungi, is a dual-specificity kinase with multiple roles in fungal biology. In this study, we assessed the roles of LkhA in Aspergillus flavus, a toxigenic fungus that produces aflatoxin B1. lkhA deletion mutants exhibited defects in fungal growth, conidiophore development, and sclerotia formation. These mutants exhibited impaired tolerance to oxidative and cell wall stresses. Moreover, the absence of lkhA resulted in a decrease in aflatoxin B1 production. The kernel assay revealed that the lkhA deletion mutants exhibited reduced production of conidia and aflatoxin B1, implying that LkhA can affect fungal toxigenesis and pathogenicity. Taken together, these results demonstrate that LkhA is important for differentiation, mycotoxin production, and pathogenicity in A. flavus.