James B. Hill, supervising architect of the U.S. Treasury Department, designed the building in the Italian Renaissance Revival style.

Supervising Architect William Martin Aiken designed a 9,000-square-foot (840 m2) addition that was built to the north of the original building in 1897.

In 1908, Supervising Architect James Knox Taylor designed two additional wings, which wrapped around the east and west sides of the building and totaled 16,000 square feet (1,500 m2), to accommodate postal service needs.

[2] Despite the enlargements, both the postal service and the court vacated the building in 1932 for other facilities in Little Rock; however, federal agencies such as the Armed Forces Examining and Entrance Station continued to occupy it.

[2] The Little Rock Post Office and Courthouse is an example of Italian Renaissance Revival architecture, a decorative style of the Victorian era.

Stone on the first level is rusticated, while the stories above are clad in smooth ashlar, an exterior treatment that is common in classically inspired architecture.

The arches have carved classical motifs, such as crests, urns, and foliated designs, and are separated by simple pilasters (attached columns).

The wide overhanging eaves are supported by ornamental brackets, a characteristic of Italian Renaissance Revival architecture.

Decorative bands and motifs are distinguished by vivid shades of paint, which were commonly used during the Victorian era when the original portion of the building was constructed.

When the ceiling was repainted as part of the 1994 to 1997 restoration, meticulous paint analysis revealed that more than 25 different colors were originally used and these were replicated.

[2] As part of the 1994 to 1997 renovations, GSA commissioned Jim Sanborn to create a work of art for the plaza sidewalk adjacent to the building.

Entitled Ex Nexum, the sculpture consists of a text-inscribed serpentine bronze screen flanked by two tall blocks of granite.