Hibs and Hearts are warning their fans not to buy tickets for the eagerly awaited match at Hampden from rogue websites.
The tickets for the south stand are being sold for up to £190 despite a face price of just £35.
A consumer watchdog and the Scottish Football Association (SFA) have encouraged fans not to use Spanish-based site LiveFootballTickets.com.
It is understood the site has been reported to the SFA’s legal team, who could take action against it.
The tickets have yet to be distributed to the Edinburgh clubs for the 19 May final.
It site says the “Face value of a ticket can differ from the selling price, because the tickets listed on LiveFootballTickets are sold at ‘market value.’”
An SFA spokeswoman said: “This is not an official site and we would advise fans not to use it.”
Both Hibs and Hearts said they were trying to ensure fans would not be exploited or miss out on the game, the first Scottish Cup showdown between the two sides in 116 years.
A spokesman for Hibs said: “Hibernian FC will do everything we can to ensure that cup final tickets go to genuine Hibs supporters and we will be working very closely with the authorities to make sure this is the case.
“That includes regular scans of social media websites and online bidding sites in an attempt to prevent touts from profiting from the phenomenal demand for tickets.”
A spokesman for Hearts said: “We will be doing all that we can to ensure fans are not exploited.
“We would encourage fans, where at all possible, to go via club channels to secure their tickets for the game.”
The demand for the tickets means season ticket holders for the two clubs will be given priority access.
Trisha McAuley, of Consumer Focus Scotland said: “We know that some sellers add mark-ups to tickets and there are also, unfortunately, some sellers who are not genuine.
“That’s why we would always urge people to be careful before buying tickets online, check official football club websites, they will have details of where to buy tickets, how much they are and what tickets are available.”
The site did not respond to a request for a comment.