Increasing demand for electronics leads excess heat dissipation inside narrow enclosures. This problem requires accurate thermal analysis of an electronics unit in order the system works properly throughout the mission. The first step for performing an accurate analysis is to set up the correct analysis model. The input parameters for the analysis such as heat dissipation from components, thermal contact resistance between the components and the board etc. usually have some uncertainties in practical applications. Those uncertainties must be eliminated in order to have a correct analysis model. In this paper, verification of the thermal analysis model of a simple electronics board with two heat dissipating components in natural convection environment is performed. Within the scope of the study, a thermal test is carried out whose results are used for tuning the input parameters which have uncertainties. After the correction process, that is, after tuning the uncertain parameters, the analysis model is verified with another test at different configuration in order to verify that the correct analysis model is set up. For the thermal analyses, a commercial finite element software is used. Results of the second analysis and the test which are performed at the verification step match within an acceptable error range. By this inference it can be said that the analysis model with the foregoing corrected parameters can be used for further different configurations and different power dissipation conditions for estimating the thermal performance of the electronics unit.