The dynamic behaviour assessment of buildings is usually carried out involving several simplifications, such us omitting the soil-structure interaction (SSI) effects. However, several studies have concluded that the SSI can worsen the behaviour of tall buildings over soft soils. Hence, in this work, the SSI effects have been considered to assess the dynamic behaviour of a case study tall reinforced concrete (RC) building. To do so, time-domain incremental dynamic analyses have been carried out. A 3D model of the building has been developed in the OpenSees framework. Nonlinear springs have been used to simulate the soil-pile interaction. The case study building is located in Seville (Spain). It was constructed prior to the Spanish seismic codes and it is located on alluvial soil. The results of the complete SSI model have been compared with the numerical analyses of the fixed-base hypothesis. Numerical results showed that this case-study will not comply with the seismic safety requirements. Static analyses demonstrated that the damage can be worsened by up to 12%, if the SSI is considered. Dynamic analyses revealed that, at the lower storeys, there is a risk of severe damage and of the collapse of the columns, which is increased up to a 22%, if the SSI is considered.