The Ulu Masen, covering 738,000 ha, stated as last remaining great wilderness in Southeast Asia. By IUCN category this area is stated as protected areas. This area having ecological value as habitat for a cryptic top predator, Sumatran Tiger as critically endangered species and facing the threat of the decreasing population caused by loss habitat through and illegal hunting. On 2012, a camera trap survey detected 9 individuals of Sumatran tiger in area. On 2013, permanent Forest Management units (FMU) were established. After 2012, there was no information about the density of Sumatran tiger and its habitat. In 2017, the camera trap survey coupled with collaborative monitoring activities between FMUs and community ranger conducted. The result showed 3 individuals of Sumatran tiger and found various wildlife trap units installed. On the same period, the evaluation of Management Effectiveness (ME) conducted to the FMUs. The result showed that there are issues on management effectiveness including the capacity of FMU in conducting forest patrol and wildlife inventory is needed. The performance of FMUs using METT is less effective. We suggest various competencies of FMUs must be increased particularly related to forest monitoring and wildlife patrol regarding protecting Sumatran Tiger and its habitat.