This study assessed the selected medicinal plants in selected municipalities of Agusan del Sur through ethnobotanical study and phytochemical screening. Findings revealed 71 plant species comprising of 36 families and 65 genera used in 14 different disease categories. Lamiaceae, represented with 6 species, had the highest Family Importance Value index. Blumea balsamifera was the most cited plant used to treat respiratory diseases and gastrointestinal disorders. Highest Informant Consensus Factor was for Category VIII or diseases of the respiratory system. Leaves were the most frequently used part in this study due to the accessibility in obtaining these parts. Decoction, employed alone or in combination, was the most common method of preparation. Four plants, Acmella grandiflora, Anodendron borneense, Hellenia speciosa, and Homalomena philippinensis, were used for phytochemical screening. Presence of alkaloids was detected for A. grandiflora. Presence of steroids was evident in A. grandiflora, A. borneense, and H. philippinensis. Presence of flavonoids was evident in A. borneense. Presence of saponins was evident in H. speciosa and H. philippinensis. Presence of condensed tannins was evident in A. grandiflora and H. speciosa. This study concluded that traditional knowledge was still being practiced among Agusan Manobo tribe as indicated in the high percentage of middle and younger age group informants. Most of these plants were safe to use and readily available as they were cultivated. It was recommended to consider thorough study on the biochemical activities, quantitative analyses, and methodical phytochemistry of novel medicinal plants and to intensify policies and priorities to promote conservation and protection of these plants.