Closely spaced tall buildings are common in modern urban areas due to limited supply of land to accommodate rapid growth of population. These buildings are vulnerable in seismically active regions particularly when earthquake-induced pounding occurs between adjacent buildings, resulting in high floor acceleration spikes that may lead to excessive demands on building contents (BCs). This paper examines the effect of seismic pounding on damage to adjacent reinforced concrete (RC) frame–shear wall buildings and their freestanding contents using nonlinear response-history analyses (RHA). A cascading analysis approach is adopted to obtain absolute floor accelerations of pounding tall buildings, which are then applied to determine response of freestanding contents dominated by either sliding or rocking motions. In order to provide a useful tool for practicing engineers and facilitate analyses, the buildings are simplified as story-based multiple-degree-of-freedom (MDOF) flexural-shear models, and unanchored contents are idealized as single-degree-of-freedom (SDOF) oscillators, all of which are approximated using OpenSees and verified against solutions to their exact equations of motion solved using Matlab. It is shown that seismic pounding leads to higher building damage and alters story damage distribution patterns. It is concluded that pounding significantly increases sliding potential and maximum sliding displacement demands on stocky contents, especially those on higher floors. The transitions of stick–slip response of the contents coincide well with pounding occurrences. It is also concluded that pounding has detrimental effects on slender rocking contents, but rocking rotation histories of these contents do not show abrupt changes upon impact.