Souza (26-6, 1 NC), who has been promised a shot at the middleweight championship with a victory, hit the scale at 185.5 pounds. Hermansson (19-4) weighed 185.
The 39-year-old Souza, out of Brazil, is a former Strikeforce middleweight champ and has won multiple gold medals at the World Jiu-Jitsu Championships and the ADCC Submission Wrestling World Championships.
Hermansson, 30, a native of Sweden who fights out of Norway, has won three fights in a row, all by stoppage.
All fighters in the card's 13 bouts successfully made weight Friday.