After the Taunus Railway (Taunus-Eisenbahn) from Frankfurt was completed to Wiesbaden in 1840, a private company was founded to continue the line along the Rhine.

The first section of the line from Oberlahnstein to Bad Ems was opened on 1 July 1858, but shortly afterwards it was buried by a landslide.

While the whole line was duplicated at that time, several sections between Koblenz and Limburg were rebuilt with single track after the Second World War, between Niederlahnstein and Hohenrhein, between Dausenau and Nassau and between Fachingen and Balduinstein.

Signs of the war-time damage are still recognisable today on the tunnels as well as on the abutments and pillars of the Lahn bridges, Weilburg station was renewed and given disability access in preparation for Hessentag 2005.

[2] The working community has set itself the goal of rehabilitating the signal box and, in the longer term, preserving it as a monument of the railway history in the Lahn valley for posterity.

In 2015, the signal technology on the Rhineland-Palatinate side (Diez–Niederlahnstein section) was modernised; the old mechanical and relay interlockings were taken out of operation, including signals and level crossings, on 24 August 2015 and replaced by a new electronic interlocking called Untere Lahn (lower Lahn) based at Diez station.

Because of new safety regulations, a wider cross section is required for many tunnels in order to be able to lay out rescue routes next to the tracks.

The stations of Albshausen and Stockhausen are to be comprehensively rehabilitated in the future by means of a subsidies provided by the state of Hesse.

A curiosity was the Frankfurt–Cologne express, which ran between Weilburg and Limburg on the Lahn Valley Railway only on workdays and only in one direction.

The traffic on the Lahn Valley Railway was a mixture of locomotive-hauled trains and diesel multiple units.

With the use of the class 215 and 218 sets, the locomotive-hauled trains were finally converted to push-pull operations, which until then had been used very rarely in the Lahn valley.

The operation of class 611 sets equipped with tilting on a continuous Regional-Express service commenced for a few months from about 1997.

After the 2006/2007 timetable change, there were separate Vectus DMU services between Limburg and Gießen: from Monday to Friday in the evening two Regionalbahn train pairs were operated by Vectus between Limburg and Giessen; several services also operated at the weekend.

Since the timetable change in December 2008, Regional-Express services have been provided by class 612 DMUs with active tilting technology, which allowed travel times between Limburg and Gießen to be shortened by about eleven minutes.

[8] Since the end of October 2009, two incidents in relation to the tilting system led to it being switched off, delaying trains by about 10 to 15 minutes.

As a result of the 2006/2007 timetable change in December 2006 and the associated cost-cutting measures in the regional transport sector, there were considerable cuts in services on the line at the beginning and end of the day.

Many goods yards and the extensive system of track that existed before the turn of the century were largely eliminated.

The situation has changed since the 1980s as all trains for the transport of clay mined in the Westerwald and bound for Italy have since the closure of the Brexbach Valley Railway between Engers and Siershahn travelled via Limburg.

These trains then run over the Main-Lahn line to Frankfurt, Mannheim and Basel, mainly continuing to Domodossola in northern Italy.

Clay is transported by truck from the mines in the adjacent Westerwald to Löhnberg station, where it is loaded on the Lahn Valley Railway.