The objective of the study was to determine growth performance, serum lipids, and intestinal volatile fatty acids (VFA) concentrations in pigs fed flaxseed meal (FM)- and oat hulls (OH)-containing diets. Forty-eight Genesus [(Yorkshire-Landrace) × Duroc] barrows with initial BW of 25.0 ± 0.32 kg were penned in pairs. Pigs were allotted to 3 experimental diets: (corn-soybean meal-based diet (Control), 12% FM- and 10% OH-containing diets, in a completely randomized design, to give 8 replicates per treatment. Diets were formulated to be iso-energetic. However, incorporation of FM and OH increased the soluble fiber (sDF) and insoluble fiber (iDF) content of the diets, respectively. Feed intake and BW of pigs were measured weekly for 28 d. On d 28, blood samples were collected via jugular vein puncture for measuring concentration of serum lipids. Pigs were subsequently slaughtered for ileal, cecal and colonic digesta collection for VFA analysis. Pigs fed the control and OH-containing diet had greater final BW (P < 0.01), feed intake (P = 0.01) and weight gain (P < 0.01) than FM-containing diets-fed pigs. Feed efficiency was reduced by 15.6% in pigs fed FM-based diets compared with the control (P = 0.01). Total cholesterol was reduced (P < 0.01) more in pigs fed OH-containing diets (1.99 mmol/L) than in FM-containing diets (2.25 mmol/L), compared with the control (2.36 mmol/L). Pigs fed FM- and OH-containing diets had greater (P < 0.01) cecal pooled VFA concentration (135 and 126 mmol/L) than those fed the control diet (87.5 mmol/L). Dietary inclusion of FM and OH increased the cecal (P < 0.01) and colonic (P < 0.01) concentration of acetate by more than 100% and 20%, respectively. A similar trend was observed in the colon in which case pigs fed the FM- and OH-containing diets tended to have highest concentrations of valerate (P = 0.09) and pooled VFA (P = 0.10). In conclusion, iDF reduced serum cholesterol more than sDF and the former depressed growth performance by reducing feed intake. However, both sDF and iDF induced variable effects on VFA concentrations depending on intestinal segment.