Stac Lee rises to 172m (564ft) above the North Atlantic and Stac an Armin to 196m (643ft).
St Kildans harvested gannets and great auks from the cliffs of Stac an Armin. St Kilda's last 36 residents left the islands in the 1930s.
At the weekend, Assynt Mountain Rescue Team members Bob Kerr, of Portskerra, and Tim Hamlet, of Achiltibuie, climbed to the summits of both sea stacks.
The pair, who were among 12 climbers working together, managed to make their climbs during a spell of fine autumn weather.
Mr Kerr said the dry conditions made negotiating droppings left by thousands of seabirds on Stac Lee a little easier.
He said: "The ascent up and along the exposed ledges and the summit slope involved stepping on and moving up through abandoned gannet nests.
"Thankfully there had been a period of relatively dry warm weather in the days before this trip and this resulted in the guano in the nesting areas being fairly dry and stable.
"We would not enjoy ascending these slopes if the guano had been wet as it would have been excessively slippery."
Once on the top of Stac an Armin, the two climbers were able to take in clear views of St Kilda and the Western Isles.
Mr Kerr said: "The views across the entire St Kilda archipelago were awe inspiring as Boreary, Stac Lee, Stac Levenish, An Dun, Hirta and Soay could all be seen from the one spot.
"The hills of Harris were also visible on the far horizon."
The remote archipelago of St Kilda is home to the UK's highest sea stacks.