Gari is a creamy white granular flour produced from fermented and gelatinized cassava mash. Application of Near-infrared spectroscopic techniques in analyzing the chemical and functional properties of gari depends on the collection of quality spectral data. This SOP was developed to collect the spectra of gari using the NIRS equipment. Particle sizes of gari vary depending on the size of the sieve used during production. Therefore, the SOP covered the presentation of gari sample “as is” and as “milled gari” to obtain the uniform particle size. Spectral data of gari were collected in three replications, and each measurement involves taking fresh samples into the sampling ring cup. The SOP also included the materials required, repeatability test and the critical points for the measurement.