Para rubber is one of the most important economical plants of Thailand. However, many farmers encounter the reduction of both quality and quantity of rubber latex caused by Phytophthora leaf fall and pot rod. This study aimed to evaluate endophytic fungi in para rubber roots and their possible antagonistic activities against pathogenic fungus, P. botryosa. Roots of para rubber were collected from 5 random areas of farmer’s field in Ban Kha District, Ratchaburi Province. Endophytic fungi were isolated from surface sterilized root tissues. A total of 107 isolates were found and 22 isolates of there were identified by dual culture test to have the efficiency in inhibiting P. botryosa more effective than 0.1% Metalaxyl. The four most effective isolates this series from namely S2P81-1, S2P12-1, S2P31-2, and S2P13-1 were then further tested for their antagonistic ability against the fungi P. botryosa on leaves of para rubber. These four endophytic fungi isolates were also tested for their efficiency on RIMM 600 rubber trees, which was expressed as the percentage of inhibition of the para rubber growth. The results have shown that endophytic fungi (S2P13-1and S2P31-2) as well as 0.1% Metalaxyl caused similar percentages of inhibition of the fungi P. botryosa growth on para rubber tree.