Tuber rot is one of the important diseases in onion caused by Fusarium oxysporum. Endophytes are biological agents that are currently widely used in controlling plant diseases. Excessive use of pesticides and continuously has shown negative impacts such as resurgence, resistance to pests and pathogens, and the death of natural enemies. Currently, pests and pathogens control effort are directed at the utilization of natural enemies or better known as biological control. Endophyte is a microorganism that grows in plant tissues without causing symptoms. Endophytes allegedly capable of producing a variety of phytochemical compounds generated by their host. The leaves of Jatropha (Jatropha curcas L.) is one part of the plant that contains secondary metabolites.Phytochemical tests on the Jatropha show that Jatropha contains alkaloids, flavonoids, and saponins that are an antimicrobial potential of plant-pathogen control agents. This study aimed to determine the effect of some Endophytes isolates and their impact on the growth of F. oxysporum in vitro in onion.Exploration (endophyte isolation from Jatropha healthy leaves) and observation (antagonist test of Endophytes of the Jatropha leaves) method used in this study was a Completely Randomized Design (CRD) with a single factor (10 treatment) repeated three times. There were 14 endophytes isolated from Jatropha leaves with a growth ratio of 4.5 cm/2 days. The best treatment to inhibit the growth of F. oxysporum in vitro is Jc5, Jc8, Jc10.