Due to the increase in computer rack equipment power in recent years, thermal management of data centers has become a challenging problem. Data center facilities with raised floor plenums are the most popular configuration from a thermal management perspective. Considerable ongoing research efforts focus on optimizing the room layouts and equipment design in order to achieve the desired cooling. However, the detrimental impact of underfloor blockages, which occur widely, is seldom addressed. These blockages often take the form of chiller pipes, cabling, and wires. They impede the flow of cold air from the air conditioning units and yield unpredictable and undesirable air flow patterns. In this paper the effect of such underfloor blockages on data center performance is characterized in detail. A representative data center is modeled using a commercial computational fluid dynamics code with typical underfloor blockages. Blockages are shown to have a significant impact on tile flow rates and rack inlet temperatures. Based on the detailed numerical study broad guidelines are presented on managing the underfloor blockages for improved data center performance. Established guidelines are experimentally validated on a different data center cell. A detailed comparison between the experimental and numerical results is presented. Based on the numerical and experimental study it is concluded that blockages if placed in “critical” path can potentially have a detrimental impact on data center performance. Case studies are presented where blockages in “safe” path will have a minimum effect on data center performance.