This study investigated the inhibitory effects of Lactobacillus casei AST18 as a biocontrol agent on fungi spoilage in yogurt. In a yogurt preservation period experiment and mould-proof accelerated testing at 4 C, the addition of 2% (v/v) L. casei AST18 in yogurt completely inhibited mould growth; mould growth was significantly delayed and spore germination was inhibited at 30 C.