Whangarei is a relatively late Troup class C station building. A large structure of rectangular form with a large verandah, it has exterior cladding of rusticated weatherboards and a corrugated-iron roof. The wide verandah has twin railway-iron posts and a sawtooth valance. The main building is divided by a concrete wall. There are a number of chimneys across the roof. Decoration is minimal, but there is a simple flared motif picked out in the gable end. The windows are largely sash with multi-pane upper lights. The platform elevation has numerous entrances and windows along its length. The interior has been altered over the years but much original fittings and joinery remain, particularly the doors and windows.
The station building is Whangarei's third. The North Auckland Line opened as far as Whangarei in 1880 and it is likely the town's first station dated from then. A contract for a new station building was let in 1902/3 and the new building was attached to the old lean-to structure. However, with the imminent completion of the line to Auckland, planning began in 1922 for a major station rearrangement and a new station building. Completed in 1925 to coincide with the opening of the line, the new building reflected Whangarei's growing regional importance. From 1939, when the parcels office was partitioned and lockers added, the interior has been the subject of successive alterations. In 1968 the Road Services depot was relocated to the station, with consequent additions and alterations. Today the building has no residual railway use, and is largely empty.