A simple and rapid method for the determination of free fatty acid (FFA) content in brown rice using Fourier transform infrared spectroscopy (FTIR) in conjunction with second-derivative treatment was proposed. Ground brown rice (10 g) was soaked in toluene (20 mL) for 30 min, and the filtrate of the extract was placed in a 1 mm CaF2 liquid cell. The transmittance spectrum of the filtrate was recorded using toluene for the background spectrum. The absorption band due to the Cdouble bond; length as m-dashO stretching mode of FFAs was detected at 1710 cm−1, and the Savitzky–Golay second-derivative treatment was performed for band separation. A single linear regression model for FFA was developed using the 1710 cm−1 band in the second-derivative spectra of oleic acid in toluene (0.25–2.50 g L−1), and the model displayed high prediction accuracy with a determination coefficient of 0.998 and a root mean square error of 0.03 g L−1.