<jats:title>Abstract</jats:title><jats:p>Three new compounds, hypoxyloamide (<jats:bold>1</jats:bold>), 8‐methoxynaphthalene‐1,7‐diol (<jats:bold>2</jats:bold>), and hypoxylonol (<jats:bold>3</jats:bold>), together with seven compounds isolated from nature for the first time, investiamide (<jats:bold>4</jats:bold>), hypoxypropanamide (<jats:bold>5</jats:bold>), hypoxylonol A (<jats:bold>6</jats:bold>), investienol (<jats:bold>7</jats:bold>), 2‐heptylfuran (<jats:bold>8</jats:bold>), (3<jats:italic>S</jats:italic>)‐5‐methyl‐8‐<jats:italic>O</jats:italic>‐methylmellein (<jats:bold>9</jats:bold>), (4<jats:italic>R</jats:italic>)‐<jats:italic>O</jats:italic>‐methylsclerone (<jats:bold>10</jats:bold>), along with 19 known compounds, <jats:bold>11</jats:bold>–<jats:bold>29</jats:bold>, were isolated from the culture broth of <jats:italic>Hypoxylon investiens</jats:italic> BCRC 10F0115, a fungal endophyte residing in the stems of an endemic Formosan plant <jats:italic>Litsea akoensis</jats:italic> var. <jats:italic>chitouchiaoensis.</jats:italic> The structures of the new compounds were established by spectroscopic methods, including UV, IR, HR‐ESI‐MS, and extensive 1D‐ and 2D‐NMR techniques. Of these isolates, <jats:bold>2</jats:bold>, 8‐methoxynaphthalen‐1‐ol (<jats:bold>15</jats:bold>), and 1,8‐dimethoxynaphthalene (<jats:bold>16</jats:bold>) showed nitric oxide (NO) inhibitory activity with <jats:italic>IC</jats:italic><jats:sub>50</jats:sub> values of 11.8±0.9, 17.8±1.1, and 13.3±0.5 μ<jats:sc>M</jats:sc>, respectively, stronger than the positive control quercetin (<jats:italic>IC</jats:italic><jats:sub>50</jats:sub> 36.8±1.3 μ<jats:sc>M</jats:sc>). Compounds <jats:bold>2, 15</jats:bold>, and <jats:bold>16</jats:bold> also showed interleukin‐6 (IL‐6) inhibitory activity with <jats:italic>IC</jats:italic><jats:sub>50</jats:sub> values of 9.2±1.7, 18.0±0.6, and 2.0±0.1 μ<jats:sc>M</jats:sc>, stronger than the positive control quercetin (<jats:italic>IC</jats:italic><jats:sub>50</jats:sub> 31.3±1.6 μ<jats:sc>M</jats:sc>). To the best of our knowledge, this is the first report on guaiane sesquiterpene metabolites, <jats:bold>3, 6</jats:bold>, and <jats:bold>7</jats:bold>, from the genus <jats:italic>Hypoxylon.</jats:italic>