The First United Building was designed by Ar. Andres P. Luna with a rectangular plan. On the main facade is a central tower flanked by two chamfered corner towers on both ends of the building.
The three towers have the same ornamental treatments of thin cylindrical moldings running up to the square plates and continued by beveled arches that relate to the windows at the sixth floor. There are octagonal windows flanked by stout finials above the arches. A pergola with protruding rafters originating from the girder connected the bevels.
The central tower which contains the main entrance of the building has a rigid arch and capped by elongated octagons that bordered a display. The parapet on the topmost part has floral arrangement on an urn with equally distant low-relief medallions. The main entrance is located below the central tower which leads to the elevator and the stairwell. The side towers are both cut in the corners to open up the intersection.