Trading Standards warns people to be vigilant as the number of scams, especially involving fortune tellers and bogus relationships, are rising.
The Department of Enterprise estimates NI consumers are losing £100m a year to international fraudsters through postal, email, text and phone scams.
Common frauds include bogus lottery wins, prize draws, career opportunities and advance fee money transfers.
A Trading Standards spokeswoman said: "There are so many scams it's unreal."
Beverley Burns, who is tasked with raising awareness about scammers, said people needed to be careful as "there is a big problem and it's on the increase".
She said there had been a large rise in the number of phone call scams.
"We are seeing more scams from people purporting to be clairvoyants, and from people offering romance," she added.
Ms Burns said it was "very much a hidden crime".
"Very often people are too embarrassed to report it," she said.
"I have been working in Trading Standards for 25 years and if anyone said to me this was going on in Northern Ireland, I would not have believed them.
"I would never have dreamt that so many people are responding to scam mail, scam text messages and scam phone calls and scam emails."
Belfast pensioner Clara Nicol said she lost almost £1,000 when she began responding to scam mail.
Some of it came from people claiming to be clairvoyants, who suggested she would have bad luck unless she agreed to send them money.
"Those letters were dangerous and frightening," she said.
"One or two of them used to frighten me. One of them stated something about a black presence and that if I wanted to be safe I'd have to to send them (money) and they would perform rituals and so on."
One woman in County Fermanagh, who asked not to be named, lost £3,000 when she started an online relationship with a man who first contacted her through Facebook.
The fraudster claimed he was a doctor working in Afghanistan.
She said: "Half of the money was my own which I got through selling my gold, and I borrowed the rest to pay this person - it was almost my downfall.
"It nearly killed me - it nearly put me over the edge that I was foolish enough to be taken in by someone like that."
More than 1,000 people from Northern Ireland are on a so-called "suckers list" which has been complied by international scammers.
Scams inflicted on the Northern Ireland public range in value from several pounds to hundreds of thousands of pounds and affect all walks of life.
Ms Burns of Trading Standards highlighted one such case involving a woman from Lisburn, County Antrim.
"Her husband, whose name was on the 'suckers list', had passed away and she told me that he had sent off over £100,000 to scammers on a daily basis," she said.
"I then discovered that she had picked up the reins and she had started sending money as well."
People targeted by mail scammers - sometimes the vulnerable or elderly - often receive dozens of unsolicited letters each day.
Trading Standards said anyone worried about being scammed or who thinks they have been taken in, should contact their helpline on 0300 1236 262.