Abstract: The anti-inflammatory phytochemical investigation of the leaves of Illicium dunnianum (I. dunnianum) resulted in the isolation of five pairs of new lignans (1–5), and 7 known analogs (6–12). The separation of enantiomer mixtures 1–5 to 1a/1b–5a/5b was achieved using a chiral column with acetonitrile−water mixtures as eluents. The planar structures of 1–2 were previously undescribed, and the chiral separation and absolute configurations of 3–5 were reported for the first time. Their structures were determined through comprehensive spectroscopic data analysis nuclear magnetic resonance (NMR), high-resolution electrospray ionization mass (HR-ESI-MS), infrared (IR), and ultraviolet (UV) and quantum chemistry calculations (ECD). The new isolates were evaluated by measuring their inhibitory effect on NO in lipopolysaccharide (LPS)-stimulated BV-2 cells. Compounds 1a, 3a, 3b, and 5a demonstrated partial inhibition of NO production in a concentration-dependent manner. Western blot and real-time polymerase chain reaction (PCR) assays revealed that 1a down-regulated the messenger ribonucleic acid (mRNA) levels of tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), COX-2, and iNOS and the protein expressions of COX-2 and iNOS. This research provides guidance and evidence for the further development and utilization of I. dunnianum.