Officers were called to a section of Accor Stadium during the second half of Friday night's game, won 20-14 by Souths, with reports of a brawl between opposing groups of supporters in the stands.
Footage on social media sites shows a number of those involved trading blows before several security guards stepped in to stop the violence.
"Officers were told two groups of people were involved," police said in a statement.
"All involved were ejected from the venue by security. No injuries were reported."
Inquiries into the circumstances surrounding the incident are under way.
A Venues NSW spokesman told AAP two groups of 11 males were evicted via different stadium gates.
"No medical assistance was required and no injuries were reported," they said.
"Any offenders will be dealt with by police and face bans from attending future events."
A text line has been made available for people to report incidents anonymously to the security control room at all major NSW venues and is printed around all venues and displayed on screens.
The Rabbitohs' win before more than 22,000 fans at Homebush was set up by star fullback Latrell Mitchell, who filled in at five-eighth after being selected to play centre following an injury layoff.
The former Roosters premiership player rocketed a cut-out pass to winger Isaiah Tass, who tip-toed to the line for the match-sealing try.
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