The objective of this study was to understand arabinose effects on butyric acid fermentation by Clostridium tyrobutyricum in sugar-supplemented media and biomass hydrolysate. Compared to glucose and xylose, the conversion of arabinose to butyric acid was less efficient with a longer lag phase (4 d) and fermentation period (6 d), and a lower butyric acid yield of 0.26 g/g and 0.15 g/g in 5 g/L and 10 g/L of arabinose media, respectively. However, the addition of 2 g/L or 5 g/L of arabinose to the baseline medium that contained glucose (15 g/L) and xylose (15 g/L) enhanced butyric acid synthesis, resulting in 16.1 g/L and 20.3 g/L of butyric acid, respectively. Further increase in arabinose to 10 g/L in the medium of 10 g/L of glucose and 10 g/L of xylose showed inhibitory effects on C. tyrobutyricum, which suggested that high concentrations of arabinose (> 10 g/L) were not desirable. Dilute-acid pretreated corncobs that contained xylose (19 g/L) and a small amount of arabinose (2 g/L) were a feasible substrate for butyric acid production by C. tyrobutyricum, and resulted in 10.6 g/L butyric acid, which was slightly lower than in the mimic medium (11.3 g/L).