Appressorium formation pathway of Magnaporthe grisea (M. grisea) is a new target for developing rice blast controlling agent. Inhibitory activity of endophytic fungi against the appressorium formation of M. grisea was screened. Two compounds displaying the activity were isolated from Alternaria tenuissima and Alternaria sp. isolated from the leaves of Acacia mangium and were identified as alternariol monomethyl ether and (4S)-α,β-dehydrocurvularin with IC50s of 51.0 and 10.6 μg/mL, respectively. These compounds were of no practical implication due to its low activity. However, they would serve as biochemical tool to study appressorium development.