Transport Minister Danny Kennedy said the £30m upgrade to the stretch of track between Coleraine and Londonderry will be done ahead of schedule, by 24 March.
It means passengers will once again be able to travel uninterrupted from Belfast to the north west, in time for the 2013 celebrations.
"The railway line was due to open in April but I was keen for the line to be open in time for the Easter holidays and, in particular, to provide transport for all those people attending the key events at the UK City of Culture in Londonderry," said UUP minister Mr Kennedy.
"This phase of the project will allow nine return journeys per day on the line and secures the long-term future of the route.
"I also understand that following a consultation with local stakeholders Translink will be ensuring travellers can arrive in Londonderry before 9am when services are restored."
For the past nine months, travellers have had to take a bus from Coleraine while phase one of work was ongoing on the line.
Phase two of the works is planned for 2015, with the cost for both totalling around £50m.
Catherine Mason from Translink said: "We are delighted to be reopening this line in time for the Easter holiday period and hope many people will take the opportunity to travel on this very scenic part of our network.
"Huge effort has gone into getting this work done on time and on budget and praise must go to our infrastructure team and contractors for their hard work on this project. Thanks must also go to our customers for their patience and understanding during the closure period."