Northern Ireland's Department for Regional Development has signed an agreement to buy 20 new trains from Spanish manufacturer CAF.
The contract worth £105m will see CAF supply 20 new Class 4000 (C4K) trains to replace 13 older formations and operate alongside an existing fleet of 23 Class 3000 (C3K) trains delivered by CAF in 2005.
The first of the new C4K trains is due to arrive in 2011 and enter passenger service by the end of that year with the full fleet delivered by 2013.
Group chief executive of Northern Ireland Transport Holding Company and Translink, Catherine Mason said that more and more people are choosing to take the train.
"Service enhancements delivered in recent years have brought enormous benefits to passengers across Northern Ireland. These new trains will allow us to increase the capacity and frequency in order to meet the growing passenger demand and encourage even more people to take the train," said Mason.
The contract signing follows a public consultation on the new trains held in May 2008 that aimed to gauge public opinion on the design and features of the current C3K trains and future aspirations. This feedback was incorporated into the overall specifications of the new C4K model.
Following the first delivery of trains in 2011, commissioning and testing will get underway with the order due for completion by 2013.