Foyle MLA Martina Anderson is to leave Stormont and take up the position in the European Parliament vacated by Bairbre de Brun, who has stood down for medical reasons.
A formal announcement is expected later this week.
Sinn Fein is understood to have met already to ratify the move.
Senior party sources said Ms Anderson, also a junior minister, will quit her current role. The Londonderry politician first stepped into the political arena in 2007 when she was elected to the Assembly. Since becoming junior minister alongside the DUP's Jonathan Bell she has taken a strong interest in European affairs and has visited and met with leaders of the European Commission in Brussels.
While she will not be the first Member of the European Parliment to come from Derry — SDLP leader John Hume held a seat from 1979 until 2004 — she is no stranger to pioneering moves.
Ms Anderson was among the first members of her party to take up a position on the Policing Board. She has also spoken many times about her visit to the First World War battlefields in Belgium, where she attended a series of events to mark the 90th anniversary of the Battle of Messines.
The former IRA member spent 13 years in prison for her role in a terrorist campaign in the 1980s, which included the Brighton bombing of the Conservative Party conference in which five people died.