Anderson, who had dethroned eight-time champion Roger Federer in the quarterfinals in a five-set thriller, advanced to his second grand slam finals.
After the break, Anderson closed out the match on his serve 26-24, after more than six and a half hours. "For us to be out there for that amount of time, I really hope we can address this", he said.
LONDON-John Isner already had won the longest match in Wimbledon - and tennis - history.
The two players were well matched throughout and the lack of a tiebreak in the final set prolonged the match until Anderson finally broke through at 7-6 (8-6) 6-7 (5-7) 6-7 (9-11) 6-4 26-24.
Novak Djokovic was leading Rafael Nadal 6-4, 3-6, 7-6 (9) in a compelling showdown filled with entertaining points that was suspended as soon as the third set concluded at just past 11 p.m., the curfew at the All England Club.
And the friendship and rivalry between the two was evident in both of their post-match interviews, with Isner quick to congratulate the South African for reaching his first Wimbledon final.
The match between Isner and Anderson, who had been trying to become the first South African to reach the Wimbledon title match since Brian Norton in 1921, featured 102 aces, with only 22 rallies going to nine points or more.
Eighth-seeded Anderson's prize for his bittersweet victory over his former United States college friend and rival is a date on Sunday with either world No.1 Rafael Nadal or fellow grand slam giant Novak Djokovic. They traded breaks in games five and six in set number four as well and Anderson made one more push to seize another one in game nine, converting his fourth set point a few minutes later to bring the set home on own serve.
The 31-year-old is eyeing a 13th major after making the semi-finals of a Slam for the first time since finishing runner-up at the 2016 US Open. The Spaniard converted two out of three opportunities to break serve in the second set.
It was Isner who came into the semifinal without losing a service game, who was the better player in the first set.
Many would argue Anderson and Isner deserve similar recognition after the great mates warmly embraced at the net before receiving a standing ovation from tennis's most famous centre-court crowd. Isner wasted a set point in the opener.
The match was ironically labelled "pointless" by viewers who complained Anderson would be left tired for Sunday's final.