The structure and oxygen non-stoichiometry of misfit layered cobaltite Bi1.85Sr2Co1.85O7.7−δ was determined by Rietveld analysis and by thermogravimetric measurements. The heat capacity and enthalpy increments of pseudo-ternary oxide Bi1.85Sr2Co1.85O7.7−δ was measured by the relaxation time method (PPMS) from 2K to 256K, by differential scanning calorimetry (DSC) from 258K to 355K and by the drop calorimetry from 573K to 1153K. Above room temperature the temperature dependence of the molar heat capacity in the form C pm =(305.8+0.07325· T −4702536· T −2)JK−1 mol−1 was derived by the least-squares method from the experimental data. The heat capacity was analyzed in terms of a combined Debye–Einstein model. The molar entropy S m ∘ ( 298.15 ) = 317.7 Jmol−1 K−1 was evaluated from the low temperature heat capacity measurements.