Harrison, who enjoyed an impressive knockout victory over Kaitlin Young last weekend, will take on Czech Republic's Martina Jindrova in her semi-final bout.
The 32-year-old American won two Olympic gold medals in Judo, including one during the 2012 summer games in London.
Harrison will now return to the city in which she claimed her first gold as she eyes a place in the PFL women's lightweight final.
In the other semi, Brazil's Larissa Pacheco will take on Ukraine's Olena Kolesnyk.
Pacheco comes into the bout as the number one ranked fighter in her division, and will be looking to progress as she targets her first PFL championship triumph.
The Copperbox Arena in London will also host the men's featherweight play-off which includes a much-anticipated clash between England's Brendan Loughnane and American Chris Wade.
Loughnane recently defeated Ago Huskic via unanimous decision to secure his place in the play-off.
Wade, on the other hand, is through to his fourth semi-final and will looking to go all the way for the first time since joining the PFL.
The second semi-final will see Japan's Ryoji Kudo square off against American Bubba Jenkins.
The action in London will take place on August 20, just seven days after a similarly stacked card in Cardiff.
Welterweight and heavyweight play-offs will be determined at the Motorpoint Arena in the Welsh capital.
Canada's Rory MacDonald will take on Russia's Magomed Umalatov in the opening welterweight bout. The second semi-final will see Sweden's Sadibou Sy face Brazil's Carlos Leal.
Meanwhile, fellow Brazilians Bruno Cappelozza and Renan Ferreira will take on Denis Goltsov and Ante Delija in the heavyweight division.
Tickets for both event are now on sale via Ticketmaster.