Sesquiterpenoids represent a structurally diverse class of natural products widely recognized for their ecological significance and pharmacological potential, including antimicrobial, anti-inflammatory, and anticancer properties. As part of our efforts to explore bioactive secondary metabolites from phytopathogenic fungi, we conducted a molecular networking-based analysis of Bipolaris sorokiniana isolate BS11134, which was fermented on a rice medium. This analysis led to the identification of three new seco-sativene-type sesquiterpenoids (1-3) and seven known analogues (4-10), with the NMR data of compound 4 being reported for the first time. The structures of these compounds were elucidated using HR-ESI-MS and extensive spectroscopic data analysis. Notably, compound 9 significantly inhibited nitrous oxide expression in lipopolysaccharide (LPS)-treated RAW264.7 cells in vitro (inhibition rate: 84.7 ± 1.7% at 10 μM), while compound 1 (10 μM) showed a weak inhibitory effect (inhibition rate = 28.0 ± 2.4%). Additionally, we proposed a biosynthetic pathway for these compounds. This study not only expands the chemical space of the helminthoporene class of molecules but also underscores the untapped potential of phytopathogenic fungi as promising sources of structurally unique and biologically active natural products.