Photothermal therapy involves the treatment of various human organs and tissues. To facilitate this, agar-based tissues phantoms are fabricated, as their thermal properties are formulated to closely replicate those of human tissues. Agar-based mediums are cost-effective, biocompatible, and flexible, with their properties adjustable by varying concentrations. They also serve as ethical and practical alternatives for experiments. To optimize thermal properties that closely match human tissue, agar concentrations ranging from 1.5 to 4.0 g were mixed with 100 ml of distilled water. This mixture was continuously stirred at 750 RPM using a magnetic stirrer at 92 °C. The agar-based tissues phantoms are used for preclinical photo thermal therapy applications. These investigations highlight the significant potential of agar-based tissue as effective platforms. The aim is to assess the thermal characteristics of agar-based tissue, including thermal conductivity, diffusivity and volumetric heat capacity. Thermal characteristics were formulate by using the advanced Trident C-THERM device with the flex TPS (ISO-22007) technique. The findings reveal variations in thermal conductivity, diffusivity and Heat capacity based on agar concentration.