Heat transfer parameters are the most critical variables affecting turbine blade life. Therefore, accurately predicting heat transfer parameters is essential. In this study, for precise prediction of the blade temperature distribution, a conjugate heat transfer procedure is used. This procedure involves three different physical aspects: flow and heat transfer in external domain and internal cooling passages and conduction within metal blade. For the external flow simulation and conduction within metal, three-dimensional solvers are used. However, three-dimensional modeling of blade cooling passages is time-consuming because of complex cooling passage geometries. Therefore, in the current work, a one-dimensional network method is used for the simulation of cooling passages. For validation of the numerical procedure, simulation results are compared with the available experimental data for a C3X vane. Results show good agreement against experimental data. The present paper investigates uncertainties of some parameters that affect turbine blade heat transfer, namely, (1) turbine inlet temperature and pressure, (2) upstream stator coolant mass flow rate and temperature, (3) rotor shroud heat transfer coefficient and fluid temperature over shroud, (4) rotor coolant inlet pressure and temperature (as a result of secondary air system), (5) blade metal thermal conductivity, and (6) blade coating thickness and thermal conductivity. Results show that turbine inlet temperature, pressure drop and temperature rise in the secondary air system (SAS) and coating parameters have significant effect on the blade temperature.