The city hall building is in the Renaissance Revival architectural style with decorative elements taken from Art Nouveau. The main building material used is plastered brick. The building has a symmetrical facade with a protruding central section that faces Storgata and out to Porsgrunn River. The central section is composed of four decorative columns around three large arched windows, with a balcony protruding from the central window that is decorated with wrought iron Art Nouveau patterns. The recessed parts on either side of the building feature smaller windows, and the arches above the second floor windows are each decorated with the Porsgrunn coat-of-arms surrounded by pors branches.
