Bioactive compound-rich brown seaweeds are demonstrated to have numerous health benefits including anti-microbial and immunomodulatory bioactivities in the pig intestine. In this study, the immunomodulating effects of extracts of brown seaweed (Ascophyllum nodosum and Fucus serratus) were evaluated on the porcine colon using a bacterial lipopolysaccharide (LPS) ex vivo model. Approximately 1.5 × 1.5 cm of pig colon (n = 6) was stripped of its overlying muscle layer and incubated in 1 mL Dulbecco's Modified Eagle Medium containing bacterial LPS (10 μg) and seaweed extracts (1 mg). Gene expression of interleukin-8 (IL-8) and interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNFA) were measured using quantitative real time PCR. In contrast to the low level of expression of IL-8, IL-6, and TNFA genes in the colonic tissue at 0 h, LPS treatment increased (P < 0.05) the expression of IL-8, IL-6, and TNFA genes to 2.38 ± 0.86, 1.90 ± 0.66, and 1.90 ± 0.57 fold, respectively. This pro-inflammatory response induced by the LPS was suppressed by the extracts of Ascophyllum. Ascophyllum extract reduced (P < 0.05) the expression of IL-8, IL-6, and TNFA genes to 0.99 ± 0.53, 0.75 ± 0.33, and 1.01 ± 0.17 fold, and Fucus extract reduced (P < 0.05) the expression of the corresponding genes to 0.70 ± 0.32, 0.69 ± 0.38, and 1.15 ± 0.25 fold, respectively. It is concluded that the extracts of Ascophyllum and Fucus seaweeds have potential to suppress the pro-inflammatory response induced by the bacterial LPS in the pig colon.