Jenkins comes into the front-row and will win his 102nd Wales cap at the Aviva Stadium alongside Richard Hibbard and Adam Jones.
The backline remains unchanged for the trip across the Irish sea.
Blues Full-back Leigh Halfpenny will win his 50th cap aged just 25. He again lines -up in a back three alongside Alex Cuthbert and George North for a 12th straight time in the Six Nations.
"It's great to bring Sam and Gethin back into the side and it's a good opportunity for Andrew Coombs to start as well," said Gatland.
"Last weekend was a good hit out for a lot of reasons, but we still have things to work on and we know how important this game is.
"We haven't lost an away match in the Six Nations since 2011 and we have to have the belief and confidence that we can do it again this weekend.
"It's going to be tough, both sides won their opening game, we will have to be physical and take it to them.
"We feel in most tournaments we get stronger as it goes on and that will need to be the case this weekend."
WALES SQUAD TO PLAY IRELAND:
Leigh Halfpenny (Cardiff Blues), Alex Cuthbert (Cardiff Blues), Scott Williams (Scarlets), Jamie Roberts (Racing Metro), George North (Northampton Saints), Rhys Priestland (Scarlets), Mike Phillips (Racing Metro), Gethin Jenkins (Cardiff Blues), Richard Hibbard (Ospreys), Adam Jones (Ospreys), Andrew Coombs (Newport Gwent Dragons), Alun Wyn Jones (Ospreys), Dan Lydiate (Racing Metro), Sam Warburton (CAPT - Cardiff Blues), Taulupe Faletau (Newport Gwent Dragons).
Replacements: Ken Owens (Scarlets), Paul James (Bath Rugby), Rhodri Jones (Scarlets), Jake Ball (Scarlets), Justin Tipuric (Ospreys), Rhys Webb (Ospreys), James Hook (Perpignan), Liam Williams (Scarlets).