Panax ginseng Meyer is used as a medicinal plant. The aim of this study was to ferment hydroponic ginseng with Lactococcus lactis KC24 and confirm its antioxidant activity and inhibitory effect on nitric oxide (NO) production. Flavonoid and phenol contents in fermented ginseng extracts were measured. Antioxidant activity was measured by DPPH, ABTS, reducing power, FRAP and β-carotene assays. Additionally, inhibitory effects on NO production and toxicity of the fermented extract were determined using RAW 264.7 cells. Phenol and flavonoid contents increased as the fermentation time increased, and the contents were higher in hydroponic ginseng than in soil-cultivated ginseng. The DPPH assay revealed that the antioxidant activity of the 24 h fermented extract significantly increased from 32.57% to 41% (p < 0.05). The increase in antioxidant activity may be affected by an increase in phenol and flavonoid contents. At 1 mg/mL solid content, the 24 h fermented hydroponic ginseng extract inhibited NO production from 9.87 ± 0.06 μM to 1.62 ± 0.26 μM. In conclusion, the increase in antioxidant activity affects the inhibition of NO production, suggesting that fermented hydroponic ginseng may be used in the industries of functional food and pharmaceutical industry as a functional material with anti-inflammatory effects.