Abstract This study investigated the anti-inflammatory effects of cell-free supernatant of Lactococcus lactis IDCC 2301 on lipopolysaccharide (LPS)-induced RAW 264.7 macrophages. Expression of inflammatory mediators and cytokines, and the production of nitric oxide (NO) and prostaglandin E₂ (PGE₂) were qualitatively analysed. The expression of signal transductors in inflammatory cascades was quantified by western blot. Treatment with cell-free supernatant of L. lactis IDCC 2301 significantly decreased the mRNA expression levels of tumour necrosis factor (TNF-α) and interleukins including IL-1β and IL-6. The levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX-2) were also remarkably reduced in LPS-induced macrophages after the treatment. Furthermore, L. lactis IDCC 2301 reduced the levels of both dephosphorylated and phosphorylated forms of nuclear factor-kappa B (NF-κB), IκB-α, extracellular signal-regulated kinases (ERK), c-Jun amino-terminal kinases (JNK), and p38 in LPS-induced RAW 264.7 cells. Therefore, L. lactis IDCC 2301 shows anti-inflammatory activity by suppressing the NF-κB and mitogen-activated protein kinase (MAPK) signaling pathways.