Khao Sok National Park is a protected area in Surat Thani Province, southern Thailand, in the western part of Surat Thani City. It consisted of the lowlands of the lower Phuket Mountain range, of the Indo-Malayan Mountain formations. Mountains are made of limestone and mostly covered with dense, moist tropical forest species. A survey was carried out along the Khlong Sok tributary of the Phum Duang River, which joins the Tapi River that empties into the Thai Gulf. The study was conducted from March-December 2019. Samples were collected (March-May) dry season and (July-December) wet season, summing up to three collections during the research. The results showed that a total of fifteen (15) families, thirty-eight (38) genera, and one hundred and eighteen (118) species were caught and identified. Families Philopotamidae, Ecnomidae, Hydropsychidae, and Leptoceridae were the most abundant and distributed groups, forming about sixty percent (60%) of the sampled caddisflies. Two new records were also found Cheumatopsyche opposita BANKS 1931* Cheumatopsyche contexta ULMER 1951*. Water quality parameters measured include temperature, dissolved oxygen, potential Hydrogen (pH), Electrical Conductivity and water Velocity. The study assessed the composition and distribution of Trichoptera fauna in Khao Sok National Park for management and conservationpurposes.