We assessed the possible synergistic effects of fiber from sugar beet pulp and benzoic acid in growing-finishing pigs. In total, 96 growing pigs ([Landrace × Yorkshire] × Duroc) with an average initial BW of 22.8 kg were selected and provided the dietary supplements based on their BW in a 2 × 2 factorial experiment, with the respective factors being fiber (low vs. high; 140 g/kg, 160 g/kg NSP, respectively) and BA (0, 5 g/kg benzoic acid) in 6 replicate pens consisting of 4 pigs per pen. Sugar beet pulp was used as a DF sources, at 50 g/kg of the diet. All diets were formulated to contain 14.44 ME MJ/kg and 190 g/kg CP. This experiment was conducted to evaluate the growth performance, nutrient digestibility, and reduction of harmful gases and serum metabolites. The pen was considered as the experimental unit for growth performance and each pig was considered the experimental unit for gas emission and serum metabolites. The final model included the main effects of DF level and BA as well as the interaction between DF and BA. Data are reported as means ± standard error (SE). Differences were considered statistically significant when P < 0.05. There was no significant difference in feed intake (1.428). No difference was found in weight during treatments. Fiber levels affect the dry matter digestibility: it was higher in the high fiber group (79.91) than the low fiber group (78.80) (P < 0.05). Addition of BA also improved the energy digestibility (P < 0.05). No interaction was found between fiber level and benzoic acid treatment. There was no difference in NH₃, but RSH (25.0, 26.1) and H₂S (20.2, 25.5) gases emissions shows significant reduction with fiber and benzoic acid treatment. Additionally, serum metabolites, including lipoprotein (LDL: 56.25, HDL: 36.25) and cholesterol (93.25), were also apparently unaffected by these treatments. Thus, the addition of 50 g sugar beet pulp per kg of growing feed as a DF source and the addition of BA had no significant effect on the growth performance of pigs during the growth period. We now consider that 50 g of sugar beet pulp per kg of diet may have been insufficient to reduce serum cholesterol in grower pigs. The findings of this study also suggests that the metabolism of benzoic acid may differ from that of niacin.