Kelulut (stingless bee) honey (KH) possesses a wide range of benefits for human consumption, such as high nutritional value, antimicrobial potency, high antioxidant value, and can exhibit medical effects. Due to its high value, this premium honey is often adulterated with different types of cheaper sugars, causing low nutrients and potential food safety threats in the final product. This emerging problem has driven many types of research to detect adulteration in honey. However, currently, there is minimal research about sugar-based adulteration of KH in Malaysia. This study aims to determine the physicochemical and rheological properties of sugar-based adulterated KH from the species Heterotrigona Itama. Adulterated samples were prepared using pure honey mixed with different concentrations of high fructose corn syrup (HFCS), i.e., 10%, 20%, 30%, 40% and 50%. Water activity, colour, total soluble solids, pH, turbidity and viscosity of KH were determined according to Official Methods of Analysis (AOAC), Malaysia Standard, MS 2683: 2017: KH – specification (Standard 2017) and harmonized methods of the International Honey Commission. In addition, the primary sugar composition (fructose, glucose and trehalulose) was determined by high-performance liquid chromatography with evaporative light-scattering detection (HPLC-ELSD). This study shows that the increasing percentage of HFCS addition in the KH samples significantly increase (P <0.05) the total soluble solids, colour, pH and turbidity; meanwhile, the water activity is reduced significantly (P <0.05). The viscosity of honey increased gradually with HFCS and glucose and fructose content while trehalulose content decreased. This research found that the physicochemical properties of sugar-based adulterated and authentic KH can be differentiated. This data is vital for the governing bodies to ensure that KH sold in the markets are free from sugar-based adulterants.