In the present work NIR detection capacity for biocatalytic oxidation of guaiacol catalyzed by horseradish peroxidase (HRP) was evaluated. UV-vis absorbance values were established as parameters for NIR spectra calibration. HRP was treated at 30 and 45 degrees C during 5 h, diluted 100x and 200x, and subsequently applied in the oxidation of the guaiacol. The spectral bands adopted for NIR monitoring was 900-1450 nm. Absorbance variations represents the bonding or breaking of certain bonds in the guaiacol conversion and tetraguaiacol molecule structuring. Four specific intervals of the NIR spectra were analyzed (940-1000 nm/1010-1080 nm/1116-1230 nm/1240-1350 nm). The results indicate that in the spectral band studied, it is possible to monitor the formation of product in the medium using Near Infrared (NIR) spectroscopy, since high correlation values were observed when relating the UV-vis and the NIR spectra data. The highest correlation values (R-2), were observed when HRP was treated at 30 degrees C-0.1 mg/mL - 200x (R-2 0.9930) and 45 degrees C-100x-0.2 mg/mL (R-2 0.9876). The excellent correlation coefficient values obtained show that NIR can be a great alternative to UV-vis spectroscopy, which allows in situ analysis of biocatalytic reactions.