The trams are the main means of transport in the city center, and 56.8 million trips were made on the system in 2019.

[1][3] In addition to the older tram network, there is a single light rail line that was opened in October 2023.

The trams are powered with electricity conveyed by 600 V DC overhead wires, although the voltage is planned to be raised to 750 V in 2025.

This system is called HeLMi (Helsinki Public Transport Signal Priority and Passenger Information).

The MLNRV I and II series (rebuilt Valmet Nr I and Valmet Nr II units) and Škoda Artic series comprise the city center fleet, and the light rail line 15 uses bidirectional Škoda Artic X54 units.

The fully low-floor Variotram units, acquired in 1998–2003 from Adtranz (later Bombardier) and built by Transtech Oy in Otanmäki, proved to be unreliable, causing a shortage of operable trams.

Starting in 2004, HKL purchased ten Duewag series second-hand trams from Mannheim in Germany to cover for the shortage.

[15][16] Metropolitan Area Transport announced a tender in October 2023 to acquire new rolling stock to replace the aging MLNRV fleet and to support new services such as the Vantaa light rail.

[23] The Crown Bridges light rail lines will have as separate depot constructed in Yliskylä, originally due to be completed in 2026.