In the present research, the heat capacities of triphenylbismuth dimethacrylate Ph3Bi(O2CCMe=CH2)(2) were measured between T = 5.3 and 330 K with the precision adiabatic vacuum calorimeter and from T = 310 to 420 K with the differential scanning calorimeter. There revealed a reproducible anomaly from 150 to 170 K caused by structural changes in the crystal lattice, and intensive exothermic transition over the range from T = 385 to 420 K caused by the reductive decomposition with the polymerization of the sample under study. The experimental results were used to calculate the standard (p = 0.1 MPa) thermodynamic functions (heat capacity C-p,m(0), enthalpy H-m degrees (T) - H-m degrees(0), entropy S-m degrees(T), and Gibbs energy Phi(m)degrees(T) of crystalline triphenylbismuth dimethacrylate from T -> 0 to 385 K. The standard entropy of formation at T = 298.15 K was calculated for the compound under study in the crystalline state. Obtained for Ph3Bi(O2CCMe=CH2)(2) results were compared with ones for Ph3Sb(O2CCMe=CH2)(2).