Aims: To compare antifungal effects of cassia oil alone and in combination with potassium chloride (KCl) or sodium chloride (NaCl) against Alternaria alternata in vitro and in vivo. Methods and Results: The inhibitory effect of cassia oil alone, or in combination with KCl and NaCl were tested in vitro. The spore germination and germ tube elongation of the pathogen was evaluated in potato dextrose broth with light microscopy analysis. The inhibitory effect of cassia oil alone, or in combination with KCl and NaCl, was determined on cherry tomatoes in vivo. The cassia oil in combination with KCl and NaCl exhibited strong antifungal effect in vivo and in vitro. Conclusions: The antifungal effect of cassia oil against Alt. alternata was enhanced significantly by combining with KCl and NaCl both in vitro and in vivo. Significance and Impact of the Study: The combination of cassia oil and KCl or NaCl may enhance antifungal effect of cassia oil and reduce cost.