Leaf mustard is rich in bioactive components such as polyphenols and glucosinolates, which reportedly have antioxidant and anti-inflammatory activities. Here, in this study, we investigated the potential antioxidant and anti-inflammatory effects of fresh leaf mustard extract (FrLME) and fermented leaf mustard extract (FeLME) using a lipopolysaccharide (LPS)-induced in vitro antioxidant model and LPS-induced RAW264.7 inflammation model. The results showed that both FrLME and FeLME exhibit antioxidant activity in ABTS, DPPH, and FRAP assays in linear. In the LPS-induced inflammatory cells, analyses of SOD and GSH-PX activities indicated that the FrLME group exhibited significantly higher activity compared to the FeLME group (p < 0.05). A comparative assessment of the extracts indicated that the levels of nitrites (NO) and inflammatory cytokines (TNF-α, IL-1β, and IL-6) were considerably lower in cells treated with FrLME than in those treated with FeLME (p < 0.05). Moreover, treatment with FrLME and FeLME effectively mitigated cellular inflammation, as evidenced by the significantly reduced mRNA and protein expression of the TLR4-NF-κB p65-COX-2/iNOS pathway markers during LPS-induced inflammation. Notably, extracts from fresh leaves demonstrated more pronounced inhibitory effects compared to those from fermented leaf mustard. The outcomes of this study establish a foundation for exploring the antioxidant and anti-inflammatory mechanisms of leaf mustard in more intricate models of inflammatory diseases. [ABSTRACT FROM AUTHOR]