PM2.5, formaldehyde, and 8 volatile organic compounds (VOCs) were observed in 6 newly decorated apartment units to evaluate the effects of the decorating process on the indoor air quality in Xi’an, China. The comparison of indoor and outdoor formaldehyde and VOCs concentrations showed that the outdoor PM2.5 concentration exceeded the indoor one during the monitoring process, whereas the indoor formaldehyde and VOCs concentrations exceeded the outdoor ones. The levels of formaldehyde and VOCs in different rooms were investigated, and the concentrations in the bedroom were found to be the highest. Furthermore, the formaldehyde and VOCs concentrations were measured in 200 other rooms decorated within a 2-year period in Xi’an, and the results indicated that wallpapering, wooden flooring, and furniture were the major decorating processes emitting these compounds. In addition, a health risk assessment of the monitored formaldehyde and VOCs in the rooms 1 year after decorating showed that benzene posed the greatest health risk among the assessed VOCs.