Synthesis and characterization of high-chain diesters have been carried out to investigate their properties for thermal energy storage applications. The synthesized compounds include diesters of octanedioic acid (suberic acid) with 1-dodecanol (lauryl alcohol), 1-tetradecanol (myristyl alcohol) and 1-hexadecanol (palmityl alcohol). While FT-IR, elemental analysis and GC-MS have been intensively used for purity control and verification, differential scanning calorimeter (DSC) and thermo-gravimetric analyzer (TGA) are the main instruments for determination of the thermal properties. Properties such as phase change temperature, enthalpy, specific heat (Cp), thermal decomposition temperatures and thermal reliability of the diesters are presented in the paper. Based on the MS data, mass fragmentation fingerprints of the compounds are also presented for chemical characterization. DSC analyses indicate that melting onset temperatures range between 37 and 55 degrees C and they have phase change enthalpy above 195 kJ/kg. The evaluated chemical and thermal data approve that the investigated high-chain diesters can be utilized for thermal energy storage and they can be named as phase change material (PCM) based on their phase change properties and reliability.