The clouded leopard (Neofelis nebulosa) is a medium-sized cat and is named after the unique cloud-like markings on its body. The clouded leopard is listed as vulnerable by the IUCN and included in CITES Appendix I. Their distribution extends from Nepal through mainland South-east Asia. To date, much of the information on the clouded leopard study is more focus on Sunda clouded leopard (Neofelis diardi). By using camera trapping techniques, clouded leopard activity pattern, relative abundance and estimate density were studied in Gunung Basor-Stong Utara Forest Reserves. The study was conducted in Gunung Basor Forest Reserve (GBFR) and Stong Utara Forest Reserve (SUFR). GBFR encompasses 516.5 km2 and SUFR 110.4 km2. A total of 69 pairs of custom built camera trap were used for this study, and set to operate 24 hours a day. About 65% of clouded leopard in the study area were photographed during the night and 35% during day, thus it can be classed into cathemeral. A total of 9,525 trap days yielded 152 photos of clouded leopard. The result of the relative abundance index of clouded leopard in the study area showed that their relative abundance index was 0.56 with standard error 0.11. From 152 photos of clouded leopard, a total of 19 individuals (14 males, 5 unknown) were identified. Based on the spatially explicit capture recapture model (SECR), the estimate density of the clouded leopard in GB-SUFC was (Dˆ ± SE) 1.15 ± 0.35 adult clouded leopard/100 km2. Data and information are vital. From the camera trapping method, this study had revealed clouded leopard activity patterns and showed their naive and robust population estimates in Gunung Basor-Stong Utara Forest Reserves. There is a need to increase enforcement and surveillance at the study sites. During our study, the level of human encroachment was high. Thus, higher frequency of patrolling would deter encroachers and poachers to commit any illegal activities.