Crowds of 3,000 and 6,000 respectively will be allowed into the Aviva Stadium for the upcoming internationals against Japan and the USA on 3 and 10 July.
It will be the first time that supporters have been admitted to the Dublin venue since February 2020.
The games form part of the Irish government's outdoor pilot sporting event programme.
Three hundred tickets for the Japan game will be allocated to frontline workers.
For the USA encounter, 25% of tickets will be allocated to rugby clubs.
The attendance of up to 3,000 fans for the game with Japan represents 5.8% of the stadium's 51,700-capacity, with that rising to 12% for the USA fixture seven days later.
The last time fans were present in the stadium for a sporting event was Ireland's 24-14 Six Nations victory over Wales on 8 February 2020.
IRFU chief executive Philip Browne welcomed the return of fans and said he hoped they would be in a position to allow greater numbers to attend the autumn internationals.
"These games are initial positive steps on the journey back to hopefully full stadia across the island," he said.
"The numbers are small, but I am sure spectators will make themselves heard in cheering on the team. We look to deliver two successful safe events, as our part in the government-approved sporting and cultural pilots in the months ahead.
"We hope that this programme, if successful, will put us all in a strong position to welcome back larger numbers of fans to the Aviva Stadium in the autumn when we will have three international rugby fixtures including games against New Zealand and Argentina."