The buildings made of ashlar masonry with ashlar facings had almost identical floor plans and elevations. They have a two-storey, gabled main building with a clock tower and a single-storey, eaves-standing side wing. After the nationalization of the private railroads in the 1880s, the Plettenberg station building was extended by a second, mirror-image side wing around 1904 to form a symmetrical complex at the time of the Royal Prussian State Railway. As part of a modernization in the 1960s, the clock on the clock tower was removed and the building was given a side extension and a continuous concrete canopy over the entire front side facing the station forecourt, which had a lasting impact on the appearance of the building.
After Deutsche Bahn gave up its use, the town of Plettenberg acquired the building and had it completely renovated at the beginning of the 21st century, taking into account aspects of monument protection (monument value justification/registration notice in the list of monuments dated 23.07.1991). The canopy was also removed and the facades were largely restored to their original state. The Ruhr-Sieg line itself was initially only upgraded to a single track, although the route for a second track had been prepared in advance. The freight volume achieved developed so positively that this second track was laid as early as 1871. The positive development continued in the period that followed - apart from economic fluctuations - and meant that the track and ancillary facilities had to be continually expanded. The connection of the Plettenberg narrow-gauge railroad (1896) and the construction of the branch line to Herscheid (1915) also contributed to this at Plettenberg station. For decades, the station was also a locomotive depot, where one or two steam locomotives were stationed for shunting operations and serving the Herscheid line. Locomotives of the Reichsbahn 74, 93 and 55 series were used.
A water tower necessary for supplying the locomotives was located on the opposite side of the station building near the goods shed. The necessary Lokschuppen was located next to the station building behind the platform towards Hagen. In addition to these extensions to the station and track facilities, a then modern horse-drawn signal box was built in 1932, but this was demolished at the end of 2006 in the course of modernization in recent years - despite being a listed building. Unfortunately, the lively industrial activity also meant that the railroad facilities were increasingly the target of air raids in the final years of the Second World War, which also led to bomb damage in the vicinity of the station, resulting in deaths and injuries. The most momentous attack took place on March 25, 1945, when a fully occupied passenger train of the Deutsche Reichsbahn was hit. This killed 13 people and 60 others were injured, some of them seriously. Despite a great deal of war damage, operations were quickly resumed.
As part of the rationalization of recent times, the closure and dismantling of the Herscheid railroad and the abandonment of general cargo and single wagon traffic have also changed the surrounding area considerably. The goods shed, the core of which still consists of the building from 1861, has been abandoned and the corresponding track systems have been decommissioned or dismantled. In 2009/10, the platform facilities were modernized for passenger transport ("100 stations in NRW" action programme) and the pedestrian tunnel was renewed, so that today there is barrier-free access to all platforms. The station forecourt was also redesigned as part of this measure. In passenger transport, the station is now served in both directions at hourly intervals by the regional express line 16 "Ruhr-Sieg-Express" and the regional train 91 "Ruhr-Sieg-Bahn" on the Essen-Hagen-Siegen route, both of which were operated by Abellio NRW until the end of 2007 and have now been taken over by DB Regio since the beginning of 2022.