Kalyan Junction is a major railway junction station on the central line of the Mumbai Suburban Railway network, lying at the junction of the north-east and south-east lines of the suburban Mumbai division of the Central Railway, 54 km (34 mi) north-east of Mumbai. It comes under top 10 busiest railway stations in India. Kalyan Junction is an important stop for all the trains. Nagpur Duronto and Deccan Queen are the two trains that do not stop at Kalyan.

Kalyan junction will get 6 new platforms under yard remodeling project. The land for this project is available in railway goods yard on eastern side of railway station. This project will ensure separation of suburban and local train operations.

One of the oldest and important railway project of Ahmednagar railway station was Kalyan-Ahmednagar railway project which was in planning stage since british regime. It was referred as 3rd ghat project. The survey of this project was carried out in 1973, 2000, 2006, 2014 etc. This project was in pink book in 2010. This project could not be started. The alignment length of thus project was 184 km and it could have been shortest route for Marathwada, Andhra Pradesh and Telangana. The major challenge for this project is 18.96 km long tunnel Malshej ghat section. Malshej Kriti samiti is following for Kalyan-Ahmednagar railway project. Kalyan-Murbad section which is first phase of this project is already under survey stage.

Towards Kasara and Khopoli, Kalyan Junction is the last station at which fast services stop i.e. all services running from Chhatrapati Shivaji Maharaj Terminus to Kasara or Khopoli start halting at all stops beyond Kalyan. The same is true for when the trains are running towards C.S.M.T., with Kalyan being the first fast stop.

Even before the Bori Bunder-Tannah line opened on April 16, 1853, further progress was already underway. The extension beyond Tannah required the navigation of the two Tannah Creeks, and tunnels in the Godadunghur hills all the way till the Parseek point (Under today's Parsik Hill). This section was let out to contractors William Whythes and Jackson all the way back in April 1851, at a cost of Rs. 3,41,407, and was completed by December 1853. The section further ahead to Callian was let out to a Parsi contractor Mr. Jamsetjee Dorabjee in May 1852, for a cost of Rs. 1,65,851 and was completed by April 1854. The line to Callian opened finally on 1 May 1854.

The first journey to Callian from Bori Bunder was scheduled that day to begin at 4:50 p.m, with Lord Elphinstone accompanied by around 250 guests. The journey proceeded, with a halt at Bhandoop to fill in water. The train finally reached Callian at 6:10 p.m, however, it did not go all the way till the station, rather only to the comparatively nearer Creek ground. Similar to the first train journey of 1853 from Bombay to Tannah, at the destination were bands, decorative tents, and a dinner. The celebration was concluded with a display of fireworks, with the train leaving for its origin at 9 p.m., reaching two hours later at 11 p.m.

There are 7 platforms at Kalyan Jn. Platform 2&3, 4&5 and 6&7 share a common platform base. Platform 4,5,6,7 serves for Express trains. Platform 5 serves for all Chhatrapati Shivaji Maharaj Terminus-bound Fast local trains where Platform 4 serves for all Khopoli/Kasara bound Fast local trains. Majority of trains towards Nashik side from Chhatrapati Shivaji Maharaj Terminus stops at platform no. 4. Platform 1 and Platform 1A are dedicated to Slow local trains that start from Kalyan and go to CSMT.

The Kalyan Electric Loco Shed and Kalyan Diesel Loco Shed are also located nearby. They are the lone sheds serving Mumbai region.

On November 8, 1991, a bomb exploded on a train when it reached Kalyan railway station. Twelve people were killed and 65 injured in the explosion. Ravinder Singh alias Bittu who was linked to the Babbar Khalsa, a Sikh militant organization was convicted in the case.

• Kalyan travel guide from Wikivoyage