The 38-year-old joined Al Hilal on Monday after reports said he turned down an offer to extend his contract with Al Ittihad, who he joined on a free transfer in 2023 after 14 years with Real Madrid.
The former France striker made an immediate impact for his new side as he broke the deadlock in style with a back-heel touch after seizing on a loose ball inside the area shortly after the half-hour mark.
Benzema doubled the score with a low, close-range drive in the 60th minute and four minutes later completed his hat-trick with another close-range effort.
The Frenchman set up Malcom for Al-Hilal's fourth, shortly before being substituted in the 71st minute.
"It was an important game today. So we are happy, we play well, we do a clean sheet and we score so we are happy," Benzema said.
"Everybody is good with me, they give me everything, so when I am on the pitch I give everything for them," he added.
Salem Al-Dawsari, the AFC Player of the Year for 2025, completed the rout with a brace.