The Neumünster–Heide–Weddinghusen–Karolinenkoog line was opened on 22 August 1877 by the Westholsteinische Eisenbahn-Gesellschaft (West Holstein Railway Company).

In Karolinenkoog a steam ferry connected to the port of Tönning in Eiderstedt (see Heide–Karolinenkoog railway).

Passenger services in the 1970s and 1980s were operated with class 515 railcars and then with less comfortable railbuses because the bridge over the Kiel Canal did not allow for higher axle loads.

After peripheral rationalisation, the operator of the Hamburg-Altona–Neumünster railway (AKN Eisenbahn) took over both the operation of rail traffic and the management of the track infrastructure in 1993 from Deutsche Bahn, initially on a trial basis with a ten-year lease.

Since the timetable change in December 2011, the line has been operated by NBE Nordbahn Eisenbahngesellschaft mbh & Co. KG, a joint subsidiary of AKN Eisenbahn AG and BeNEX GmbH.

At the time of the acquisition of the SHB by the AKN, it also terminated the lease of the Neumünster–Heide line.

Due to the extended travel times, the scheduled meeting of trains at Heide and Neumünster stations under the regular interval timetable could not be fully achieved.

In the course of the modernisation of the line, however, the old station building in Wasbek, Aukrug, Osterstedt, Gokels and Nordhastedt were demolished.