The Yorkshireman resigned as chief executive of the Ibrox side in April but will now help to "promote the interests" of the Light Blues.
He quit the club amid allegations of links with discredited former owner Craig Whyte at the time of the Green consortium's acquisition of Rangers.
A brief statement from Rangers to the Stock Exchange confirmed: "The board of Rangers is pleased to announce that it has today appointed Charles Green as a consultant to the company.
"Mr Green's role will be to promote the interests of Rangers Football Club, specifically assisting with shareholder relations and advising the company on its capital structure."
The consortium led by Green purchased the business and assets of the club last summer after liquidation was confirmed, following several months in administration.
Green strenuously denied any wrongdoing at the time of his resignation.
An independent investigation commissioned by the Rangers board subsequently found no evidence that Whyte had invested in the current Ibrox set-up.
- Rangers Football Club
- Craig Whyte