Antimony (Sb) contamination has become an increasing environmental concern. A pot experiment was conducted to investigate the effects of biochar application on the maize seedling grown in Sb-contaminated soil. Two Sb levels (0, 200 mg kg−1) and three biochar rates (0, 1%, 4%) were included, giving a combination of six treatments. The results showed that exposure to Sb without biochar application (Sb2BC0) induced undesirable effects on maize seedlings, such as the inhibited growth of leaves, stems, and roots; the disorder of antioxidant system; and the reduced uptake of nutrients. Compared with Sb2BC0, biochar application to Sb-treated plants alleviated the negative effects of Sb, possibly due to the following findings: (1) the enhanced activities of SOD, POD, and CAT and the increased leaf chlorophyll content while accompanied with the reduced MDA content; (2) the increased N, P, and K content in both shoot and root; (3) the decreased shoot Sb accumulation due to the reduced translocation efficiency from root to shoot. In contrast, biochar application to nil Sb-treated soil had no significant effect on maize growth. Biochar application also immobilized soil Sb by transforming the relatively available fractions to geochemically more stable Fe and Al oxides bound fractions. These results indicated great potential of using biochar to reduce soil Sb availability for Sb-contaminated soil.