Development began in September 1996 with the helicopter officially announced by Eurocopter at the Paris Air Show in June 1997.

The first EC155 helicopter, a modified Dauphin airframe, made its maiden flight at Marignane on 17 June 1997 and the first pre-production EC155 B flew on 11 March 1998.

The aircraft received safety certification by the French and German civil aviation authorities on 11 December 1998 and went into production soon after, with a price tag of US$7–8 million depending on installed equipment.

In early 2003, Eurocopter completed studies for an even more powerful version of the EC155 B1, designed to better compete with new rotorcraft such as the AgustaWestland AW139 and to better meet military customer's requirements.

The EC155 is to serve as the basis for KAI's Light Civil Helicopter (LCH) and Light Armed Helicopter (LAH), featuring numerous changes including a new cockpit, improved gearbox and rotor blades; the LAH shall have a chin-mounted 20 mm cannon and side-mounted guided rockets, countermeasures systems, and be able to carry 6–10 combat troops.

[6][7] The EC155 B features a completely redesigned cabin providing 30% more passenger space than previous Dauphin helicopter models, plus a 130% increase in baggage hold volume.

The EC155 is also equipped with a four-axis digital autopilot, coupled to the engine FADECs for full-envelope protection, and is offered with a Health and Usage Monitoring System (HUMS).