After watching Isner strike a tired forehand wide, Anderson advanced to the Wimbledon final at the 10th time of asking.
In a marathon match on Friday night which was the longest in Wimbledon semifinal history, lasting over five hours on court, Anderson was able to claw back from 2-1 back to seal the victory.
Two medical time-outs for the big American hinted at a chance for Anderson, and the South African took advantage with a big break and serving out to level up at two sets apiece.
Anderson served for the third set at 5-3 after ending Isner's streak of holding 110 consecutive service games at this tournament.
The first match on the Tour between these two was in Las Vegas in 2008 but they have played a very important match in Collegiate tennis back in 2007, and this is a nice occasion to go back in past and examine their Collegiate careers.
Isner appeared to be struggling at times from 12-all to 18-all, but he held firm on his serve as Anderson, playing his second-consecutive five-set match, found a second (or third or fourth) wind. However, Melichar and Peschke won the next two games to seal it.
The 32-year-old, the first South African Wimbledon men's finalist since Brian Norton in 1921, faces Novak Djokovic or Rafael Nadal in Sunday's showpiece.