On 1 October 1891, the new Wannsee Railway opened as the first suburban route in Germany, separated from the main line and having its own fare structure.

The mixing of stopping and non-stopping trains on the first section of the Wannsee line to Zehlendorf caused problems.

Suburban trains from Werder (Havel) via the Potsdam-Zehlendorf main line tracks took the same path.

After the completion of the electrification of the cross-city Stadtbahn and circular Ringbahn lines, the electrification of the Wannseebahn was begun in 1932, fitting the 18.61 km long line with third rail touched from below, and also the 12.06 km length of the mainline tracks between Berlin Potsdamer station and Zehlendorf for the Bankers trains running non-stop to the long distance station of Potsdamer Bahnhof.

After the grand opening of the underground Berlin Anhalter Bahnhof station on 6 October 1939, the merged diameter line ran thru the new tunnel between Wannsee and Oranienburg via Potsdamer Platz, Unter den Linden, Friedrichstrasse and Stettiner Bahnhof.

After a strike by West Berlin employees of the East German Railways in 1980 passenger service were not resumed on the Wannsee line.

It continued to serve, however, as a connection to the Wannsee depot for the remaining West Berlin S-Bahn trains operating through the north-south tunnel on services between Lichtenrade or Lichterfelde Süd and Heiligensee.

After West Berlin’s takeover of the western S-Bahn network on 9 January 1984 it was decided to put the Wannsee line back in operation.

Today, the Wannsee line is again an important link from the south-western residential areas to central Berlin.