The injury-depleted tourists have made four changes from their last international, a 35-25 win over Scotland in Dublin the Six Nations Championship in March, with Jackson set for a rare start.
“I’ve been waiting for a chance and now I’ve got it, I’m grateful it has come. There will be nerves but a lot of excitement,” he told a press conference on Thursday.
After he named the team, coach Joe Schmidt added: “Paddy has bided his time and will slot in really well. I think he’s got big boots to fill but he has the right-sized shoes.”
Sexton was among several significant injury setbacks for the Irish before the three-test tour but Schmidt said he was pleased with his selection.
“I’ve got a mix of experience and a lot of energy which could be significant after a long season,” he said.
“We are hoping to get a platform to build on and to get something out of this series going forward. You are never going to be in a situation where everything works out perfectly but I'm hoping to get enough confidence to build through the series.”
Jared Payne switches from centre to fullback with Luke Marshall coming in at inside centre and Robbie Henshaw moving outside of him. Leinster’s Jordi Murphy was chosen as openside flanker while Iain Henderson returns to the second row.
South African-born loose forward CJ Stander continues at blindside for a sixth successive test since his Irish debut but hooker Richardt Strauss, cousin of Springbok captain Adriaan Strauss, was not picked in the line-up.
South Africa host Ireland in the second test in Johannesburg on 18 June with the third test taking place in Port Elizabeth the following weekend.
