Ms McTernan is a teacher in Kilkenny, where Mr Phelan has been the sitting Fine Gael TD since 2011.
The pair met via Fine Gael as Ms McTernan is a long-time party activist and daughter of a well-known former Leitrim Fine Gael county councillor, John McTernan.
The wedding took place in the family's local church in Dromahair.
After the ceremony, the wedding party went on to celebrate the event at the Castle Dargan Hotel at Ballygawley in Co Sligo.
Taoiseach Leo Varadkar and his partner Matt Barrett were among the guests, as was Dublin North West TD Noel Rock and Sligo-Leitrim TD Tony McLoughlin.
Former Fine Gael minister Lucinda Creighton and her husband, former senator Paul Bradford, were also in attendance.
Mr Phelan is facing a busy year as he is national director of elections for Fine Gael in next May's local council elections.
He is also the minister responsible for local authority reforms.