In this study, the effect of shrinkage and temperature variation on the behavior of long span reinforced concrete flat plate system and raft foundation supported directly on soil or piles, has been examined via the nonlinear finite element analysis. In the analysis, shrinkage has been considered as a drop of temperature of 30   oC for the flat plate system and of 20   oC for the raft foundation. A change of temperature of uniform profile and of nonlinear gradient have been considered. The analysis accounted for material nonlinearity and it has been performed for all possible load combinations. The results of analysis revealed that material nonlinearity plays a major role in the response of the structure for temperature and shrinkage effects since its presence remarkably reduced the adverse effect of the two factors. Shrinkage and temperature variation had more significant effect on slabs than on rafts. Their effect on concrete stresses was not critical in slabs and had no significance in rafts. On the other hand, such effect on steel reinforcement was noticeable in rafts and significant in slabs. This led to the conclusion that the effect of both temperature variation and shrinkage can be accommodated by additional reinforcement. In slabs, for an accurate assessment of deflection, it is important to account for both factors in the analysis.