Sinlek, a Thai rice cultivar, has a high iron content with a low glycemic index. Advantageous properties of this rice make it a functional ingredient in food. The research objective was to develop a brownie with iron fortification by substituting Sinlek brown rice flour for wheat flour. Sinlek brown rice flour was mixed with wheat flour at 0-100% (w/w). The Sinlek brown rice flour had high protein (15.83%) and iron (12.96 mg/kg) contents, but low amylose content (11.97%). Water solubility index gradually decreased while water absorption index increased with the substitution level of Sinlek brown rice flour in flour mixes. Brownie with Sinlek brown rice flour and wheat flour at 75:25 ratio gave the highest sensory scores for all attributes. This product has a high nutritional value in its iron content. Therefore, Brownie with Sinlek brown rice flour is a recommended health product for consumers who need high-iron food.