One of the reasons on the poor quality of patchouli oil is its mixing proportion with other oils or components, which can cause the selling price much cheaper. The main objective of this research is to develop the NIRS technology to determine the content (quantification) of palm oil mixed in the patchouli oil using the chemometric analysis with the Principal Component Regression (PCR) calibration method. The materials used in the research were patchouli oil and palm oil; the NIRS of FT-IR T-1516 tool, and The Unsclamber 10.4 software. This study used seven samples consisting of 100% pure patchouli oil; 100% palm oil; and a mixture of patchouli oil and palm oil with a ratio of 50%: 50% (PcPo50%), 75%: 25% (PcPo75%), 80%: 20% (PcPo80%), 90%: 10% (PcPo90%), and 95%: 5% (PcPo95%). The results showed that using NIRS technology in combination with PCR method has the opportunity to be used as a new method for estimating the content of palm oil added to patchouli oil. The three pretreatment models that were used, namely Mean Normalization (MN), De-Trending (DT), and Standard Normal Variate (SNV), are categorized under the very good performance (RPD > 3). The MN and SNV pretreatment models are two best correction methods that produce a model with a high degree of accuracy: the value of the coefficient of determination (R²) is 0.88, the correlation coefficient (r) is 0.94, the root mean square error calibration (RMSEC) is 10.85%, and the residual predictive deviation (RPD) is 3.22.