Metal nanoparticles synthesized using the green methods are essential for utilization of the nanoparticles in diagnostic and therapeutic applications. The usual syntheses of the metallic nanoparticles often involve toxic chemicals, which limit the use of metal nanoparticles in biochemical applications. An in-situ synthesis of gold nanoparticles (AuNPs) on the rice grain surfaces using the phenolic acid content of rice as the reducing agent, and utilization of the AuNPs-decorated rice (Au-rice) as a surface-enhanced Raman scattering (SERS) substrate are demonstrated. An increase in the HAuCl4 concentration of the reaction mixture was shown to cause almost a linear increase in the size of AuNPs on the rice grains. By varying the HAuCl4 concentration, the size of the synthesized AuNPs can be adjusted between 41 +/- 13 nm and 177 +/- 38 nm. Among the as-produced Au-rice samples, rice grains with the AuNP size of 131 +/- 30 nm were found to be the most effective in the SERS analysis of 4-aminothiophenol (4-ATP). The effectiveness of the Au-rice samples as SERS substrates was demonstrated with a 4-ATP detection limit of 10(-6)M and an analytical enhancement factor (AEF) of 1.5 x 10(5).