Both former players celebrated the forthcoming Lions tour by donning their respective jerseys at the summit despite the minus 20 degree temperatures.
Gibbs described the experience as the 'hardest, most enduring event of his life' but was thrilled to have made the climb.
"Francois and the other Springboks told me it was going to be an easy hike, and yet it was incredibly difficult," said Gibbs, who played a huge role in the Lions' last series-winning tour 12 years ago.
"It was minus 20 degrees with a foot of snow which meant the going was extremely tough and slow."
Gibbs and Pienaar both completed the climb for the Make-a-Difference (MAD) charity - a Cape Town charity which helps raise funds for children from less privileged backgrounds to reach their full potential. Joining them were Hennie Le Roux and Johann Styger, who both played for South Africa during the 1990s.
"We had a blast and there was such a great dynamic between the team......plenty of banter and joke telling en route," added Gibbs.
"The summit experience was a truly emotional one coupled with the elation of such an achievement......even if I was outnumbered by Springboks! Go Lions!"
The shirts worn by Pienaar and Gibbs at the summit will be auctioned at a special MAD charity event in Durban ahead of the second Test between the Lions and Boks on June 27.