The purpose of this study was to evaluate the effects of feeding pigs with inulin and/or benzoic acid on post-weaning diarrhoea (PWD), indices of fermentation in the gastrointestinal tract, and production in pigs experimentally infected with an enterotoxigenic strain of Escherichia coli (ETEC). Forty-eight entire male pigs (Large White × Landrace) aged 21 ± 3 days of age and weighing 4.97 ± 0;0.08 kg (mean ± SE) were used in a 2 × 2 factorial experiment, with the respective factors being inulin (0 versus 8%) and benzoic acid (0 vs. 0.5%). Feeding inulin-supplemented diets improved (p = 0.022) the faecal consistency (FC) and reduced (p = 0.001) the incidence of PWD; however, the use of benzoic acid had no effects on PWD or faecal ETEC shedding. Wet faeces (a higher FC score) were associated with increased faecal ETEC shedding (R2 = 0.394, p = 0.001). Inulin reduced the total concentrations of short chain fatty acids (p = 0.029) in the proximal colon. The total concentration of lactic acid was increased by inulin in the caecum (p = 0.007) and proximal colon (p = 0.002). Feeding inulin or benzoic acid had no effects on production after weaning.