The light heavyweight contest headlined UFC Fight Night inside Ginasio Do Ibirapuera in Sao Paulo, Brazil. Blachowicz (25-8) outpointed Souza on the official scorecards 48-47, 48-47 and 47-48. ESPN scored the fight 48-47 for Souza, though it was a very close affair that could have gone either way.
Blachowicz, of Poland, likely won't land a title shot with the victory, but his title aspirations would have taken a significant hit had he lost. He improves to 6-1 in his past seven.
"I want someone from the top [next]," Blachowicz said. "Maybe a title shot. Why not? [Champion Jon Jones], let's do this. Jon, give me a shot. I don't have much time. Maybe three years before I retire. It's now or never."
Blachowicz and Souza (26-8) both had a cautious game plan for the five-round fight. Souza, 39, repeatedly tied up with Blachowicz in a clinch along the fence, where he searched for takedowns. The former middleweight simply could not get Blachowicz down, as he went 0-5 on takedown attempts, according to UFC Stats.
Souza's wrestling and overhand right clearly had Blachowicz hesitant to take risks, however. He appeared to briefly stun Souza with an uppercut in the final round but was not offensively efficient otherwise. Blachowicz also appeared to suffer an injury to his left foot midway through the bout.
Souza, who had back-to-back defeats for the first time in his storied career, said he nearly withdrew from the bout at the last minute due to illness.
"Every time it's a tough fight, they never give me decision," Souza said through an interpreter. "They never give me the win. Ten days ago, I almost had to pull out of the fight, but I had to fight in Brazil. I had to fight at home."
Blachowicz will likely finish 2019 with a 2-1 record. He suffered a TKO loss to eventual title challenger Thiago Santos in February before defeating two former middleweight titleholders in Luke Rockhold and Souza. Souza drops to 1-3 in his past four.