One Penn Plaza is built with structural steel and concrete, with grey solar glass and anodized aluminum on the outside walls.

Mechanical rooms are located on the 12th and 13th floors; placing these on lower floors instead of the top of the building allowed equipment to be installed before the structural steel framework was complete and shaved six to nine months off the building's construction schedule.

Direct passageways at each end of the building provide underground connections to the Long Island Rail Road concourse of Pennsylvania Station, which is located one block to the south.

[7] In 2009, plans were made to install a cogeneration plant in order to heat the building more efficiently.

[14][15] More than 80 percent of the action in the 2011 independent film Margin Call was shot on the 42nd floor of the building, which had recently been vacated by a trading firm.