The 28-year-old, was filmed on Saturday in a clip later shared on TikTok, which showed him speaking with a man described by a fan as a bodyguard before greeting attendees - and telling him: "Don't ever tell me what to do."
Elordi told the official, before posing for photos with fans: "I'm going to take a picture right here."
After finishing, he turned back to the apparent staff member and added: "Don't ever tell me what to do."
Despite the tense moment, the fan who posted the footage described Elordi as friendly, saying he "was so nice" and "took photos with everyone he can."
Elordi, known for his roles in Saltburn and Euphoria, was attending his first public event since splitting from Olivia Jade Giannulli, 25.
He wore a black suit with a bow tie and shoes to the screening at the Sala Grande Theatre.
The screening of Guillermo del Toro's Frankenstein – a $US120 million Netflix production – drew a 13-minute standing ovation, Variety reported.
People noted Elordi was "moved to tears" at the response as he hugged del Toro and co-star Mia Goth, 31, who plays Elizabeth Lavenza in the film, before bowing his head toward the audience.
During the ovation, del Toro, 60, embraced Elordi.
Christoph Waltz, 68, also stars in the film, playing arms merchant Harlander in the adaptation, while Felix Kammerer, 29, portrays William Frankenstein.
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