Almost £17 million of European funding has been allocated to improve tracks between Coleraine and Derry as well as Knockmore and Lurgan in Co Armagh.
Transport Minister Danny Kennedy said it was a welcome boost for his cash-strapped department.
He said: "This is great news and a further significant investment in our railways."
The line between Coleraine and Derry was hailed by Michael Palin as one of the most beautiful rail journeys in the world but work to bring it up to modern-day standards has been dogged by delay.
Mr Kennedy said: "Competition for the funding was unprecedented, with 700 applications submitted, totalling 36 billion euro of requested funding, three times more than that which was available.
"Given the level of over-subscription, my department has been extremely successful. This highlights the importance of active engagement in Europe."
Funding for the two schemes has been made available through the Connecting Europe Facility and follows a meeting between Mr Kennedy and the EU Transport Commissioner Violeta Bulc in Riga, Latvia, earlier this year.
