"Ireland can be confident of beating South Africa," said 33-year-old Easterby.
"The Lions showed in the summer that they are not invincible and they were lucky to come away with a 2-1 victory over the Lions.
"The Lions should have won the first two Tests as well and it could have been very different.
"South Africa are a great side and excellent at winning tight games and that's the way they won the World Cup.
"But in the autumn they will come off the back of a long, hard season and I've got no doubts that Ireland can continue their great form of the Grand Slam and take some major scalps."
South Africa have not recorded a victory over Ireland in Dublin since their hard-fought 28-18 victory in 2000.
And Easterby believes the success of the likes of Lions stars Rob Kearney, Jamie Heaslip and Luke Fitzgerald will continue the visitors' dismal form in the Emerald Isle.
"They are the next generation of Irish rugby and have only been in rugby a couple of years but they have already won the Grand Slam, Heineken Cup and been on a Lions tour," added Easterby, who himself won Test honous with the Lions in New Zealand four years ago.
"They've experienced a lot but been very successful in a short period of time. Jamie and Rob were fantastic in the Test series while Luke also had a wonderful tour.
"Hopefully they will grow from those experiences and face the challenge head on to maintain their standards year-in, year-out. I've no doubt they will kick-on and better themselves."
Easterby, capped 65 times by Ireland, has recently taken up a player/coach role at the Magners League side the Scarlets.
And the flanker has revealed he would be interested in rejoining the Ireland management set-up one day.
"I'd never say never but it's one step at a time. It's my first experience as a coach and I have to earn my stripes.
"Hopefully I can be successful and whatever happens will happen. I'm not ruling anything out but I have to work hard to make a success of it."