Abstract Surfactants have the ability to overcome the capillary forces restricting mobilization of oil in the porous media. Generally, the application of surfactants in harsh reservoir conditions has been avoided, due to the challenges accompanying their implementation in such conditions. In this paper, the performance of a mixture of Alkyl Ether Carboxylate (AEC) and Alkylpolyglucoside (APG) was experimentally investigated in harsh reservoir conditions. A Malaysian offshore field with challenging conditions has been studied in this present work, with a reservoir temperature of 106°C and injection water salinity of 32,000 ppm. The investigations were made using surface tension, interfacial tension and partitioning experiments. Surfactant concentration was measured throughout the partitioning test using High Performance Liquid Chromatography (HPLC). The results of the surface tension test showed that the CMC for AEC:APG mixture was approximately 0.13 wt% at 106 °C. IFT results showed that the presence of the surfactant mixture was capable of reducing the IFT between crude oil and brine, and achieve low IFT value (0.035 mN/m) in such harsh conditions. Partitioning test results explained the partitioning behaviour of the surfactant molecules into the oil-water interface. Additionally, surfactant concentration, brine/oil ratio and salinity have a significant impact on surfactant partitioning. The results corresponded to the interfacial tension behaviour, where the lowest IFT value was observed at the highest kp value for the AEC:APG mixture. This concluded that the partitioning coefficient can be directly related to interfacial tension. Furthermore, the increase of the brine/oil ratio as well as the salinity, portrayed an increasing trend of the kp values. The findings of this study showed promising outcomes for future implementation of surfactant flooding in such harsh conditions. By using the proposed surfactant mixture, potential success becomes likely for surfactant flooding application in this study under harsh reservoir conditions.