Nerys Jefford was educated at Olchfa Comprehensive School in Swansea before studying law at Lady Margaret Hall, Oxford, and at the University of Virginia, where she was a Fulbright Scholar.
She was called to the Bar in 1986 and practised at Keating Chambers in London, specialising in construction and engineering law. A large part of her practice was in international arbitration, particularly in the Far East and Middle East.
She was appointed as a Recorder in 2007 and as Queen’s Counsel (now King’s Counsel) in 2008. She was appointed a High Court Judge in 2016. In 2019 she was appointed as Administrative Court Liaison Judge for the North Eastern Circuit. In 2020 she was appointed a Presiding Judge of the Wales Circuit and she is the current Deputy Chair of the Boundary Commission for Wales.