It was the first time Celtic fans have been able to attend an Old Firm derby at Ibrox since January 2023 after an agreement was reached to resolve a dispute over ticket allocations.
"Rangers Football Club condemns the actions of the individual who threw a bottle during today's match," a Rangers spokesman said.
"This behaviour has no place at our stadium. Steps have already been taken to identify the person responsible and the club will take the strongest possible action once their identity is confirmed.
"We also acknowledge that the tifo displayed prior to kick-off crossed a line and was unacceptable. Our approach to supporter displays has always been built on trust, with the responsibility placed on groups to exercise good judgement.
"We will reflect on how these displays are managed and engage with supporter groups to ensure the right balance of trust, responsibility and oversight is maintained moving forward.
"Rangers is proud of its passionate fanbase and we all share a duty to protect the standards and reputation of our club."
A Police Scotland spokesperson told BBC Scotland: "We are aware of the banner and enquiries are ongoing."
Any potential charges brought against Rangers by the Scottish Professional Football League could depend on whether the incidents are included in the match delegate's report.