NFU Scotland said some of its members had reported calls from con-artists in recent days, particularly in the Lothians and Borders area, claiming to be from Royal Bank of Scotland and stating the farmer had fraudulent activity on their account.
Similar scams have been reported in England and Wales.
On one occasion the call appeared to be from a genuine Royal Bank of Scotland number.
When asked by the farmer to confirm their name and local branch, the caller became abusive and hung up.
The farmer has since checked with his bank and they have confirmed the call was a scam.
Police Scotland have warned farmers to be aware of the calls.
NFU Scotland’s finance director Colin Gordon said:“This is such a busy time of year for agricultural transactions that farmers could be easily caught out by alarming calls from people claiming to represent their bank’s fraud department. Do not fall for this.
“We know that if this is happening in one region it is only a matter of time before other areas are targeted and experience has shown that these tend not to be isolated incidents.
“Your bank will never phone or email you and ask for your online password information or any password using your online banking token or card and reader. They will never ask you to make a payment over the phone by using your online account.
“If you receive a call claiming to be from your bank and they suggest that you call them back, ensure you use a different phone as the caller may still be on the line without you knowing.”
Don’t give out any personal information unless you are the one who made the call and you are certain of the identity of the person you are speaking to.
Don’t give out your credit card or bank card details to strangers on the telephone.
Never tell somebody your bank PIN number, even if they claim to be the bank or police. If the caller is genuine they will never ask for this information.
Don’t give out information which may infer that you live alone, are older or vulnerable.
Never send money to anyone who claims to have a prize for you.
If it sounds too good to be true, it probably is.
To report fraud call Action Fraud on 0300 123 2040.