ABSTRACT To date, information regarding the effects of Si on rice (Oryza sativa L.) nutritional quality is rarely reported. The current study was conducted to evaluate how Si fertilizer impacts the mineral element, protein and amino acid concentrations in brown and milled rice. The experiment was a randomized complete split-plot design, with Si treatments as main plot and two cultivars as subplot. Compared with the control, application of Si fertilizer significantly enhanced the Zn, Ca and Mg concentrations in brown and milled rice but had nonsignificant effects on the Fe, Mn and Cu concentrations. Moreover, application of Si fertilizer resulted in significant increases in the concentrations of protein and most of the amino acids in brown and milled rice. However, the Gly, His, Val, Met and Lys concentrations were unaffected by the application of Si. The responses of the Cys and Phe concentrations to Si fertilizer application were cultivar-dependent. Applying Si significantly increased Zn, Ca, Mg and protein concentrations by 21.77%, 25.77%, 7.25% and 6.19% in milled rice and by 25.18%, 39.81%, 9.24% and 5.52% in brown rice. These results indicate that Si fertilizer could improve rice nutritional quality by increasing concentrations of mineral elements, protein and some amino acids in brown and milled rice.