Thai red curry paste contains several herbs and spices well known for their health benefits. The objective of this research was to study the effects of heat treatment on the antioxidant capacity (total phenolic content (TPC) and its antioxidant activity) and colors of Thai red curry paste. The paste was subjected to heat treatment at different temperatures (60, 75, 90, 105 and 120°C) and for different times (0, 10, 20, 30, 40, 50 and 60 min). The TPC was determined by the Folin-Ciocalteu method and its antioxidant activity was elucidated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidative power (FRAP) assays and expressed as Trolox equivalent antioxidant capacity (TEAC). Thai red curry paste color was expressed as Hunter L, a, b values. Results showed that heat treatment had a significant (P < 0.05) effect on the TPC, antioxidant activity and color. The samples treated at 120°C had higher TPC and antioxidant activity than the untreated samples. The color parameter L values of red curry paste increased when the sample was heated higher than 60°C, while color parameters a and b were not different for most of the heated samples.