Conventional dietary strategies to reduce pig manure odor may either be costly, or impede nutrient digestibility. Additionally, the response of manure odor to such measures may be variable, indicating a complex relationship between environmental pollutant and diet. We hypothesized that dietary Lactobacillus plantarum (LP), with or without the inclusion of a purified oligofructose (inulin), may reduce odor without compromising nutrient digestibility. An experiment with a 2 × 2 factorial arrangement of treatments was conducted to investigate effects of dietary inulin (0 and 12.5 g/kg) and LP (0 and 0.5 g/kg) on nutrient digestibility, indicators of gastrointestinal tract fermentation, select fecal bacteria, manure content, and ammonia and odor emissions of 28 growing-finishing pigs (60.3 kg; n = 7/treatment). Dietary treatments had no effect on nutrient digestibility. Dietary treatments containing inulin had decreased Enterobacteriaceae (8.60 vs. 9.67 log gene copy number/g fresh feces; P = 0.03) when compared with unsupplemented diets. There was an interaction between dietary inulin concentration and LP supplementation on estimates of fecal Clostridia (P = 0.01). Pigs offered diets containing both inulin and LP in combination had increased Clostridia when compared with those offered the control diet. However, there was no effect of either LP or inulin fecal Clostridia when offered singularly. An interaction was also noted where diets supplemented with LP or inulin only reduced odor (P = 0.01) compared with the control diet. However, there was no effect of LP on manure odor emissions when offered in combination with inulin. In summary, this study demonstrated that dietary supplementation with either exogenous LP or inulin reduces manure odor but not when offered in combination.