Of the 4,150 full-time firefighters across Wales' three fire brigades, only 40 are black and minority ethnic (BME).
Five of north Wales' 880 firefighters are BME, in mid and west Wales it is 15 of 1,390 and in south Wales it is 20 of 1,880. BME people make up 4% of Wales' population, according to the latest census.
Fire minister Mike Penning said diversity was "not an optional extra".
"Firefighters, like police officers and other local emergency services personnel, should reflect the communities they serve and we expect fire and rescue authorities to do much more to improve BME... representation," he added.
The Fire Brigades Union (FBU) said the fact just 4.4% of firefighters in England and Wales were BME was "totally unacceptable".
The figures, released by the Department for Communities and Local Government, show 10 firefighters, all in south Wales said "don't know" when asked about their ethnicity.
Although there are no statistics for a breakdown of Welsh cities, in places like Greater Manchester, just 2.8% of firefighters are from an ethnic minority compared to 16.2% of the population as a whole.
Mick Nicholas, the most senior black member of the FBU, told BBC Radio 5 live the fire service had been "inconsistent" at recruiting from non-white communities.

World number four Massaro, 33, won 11-8 12-10 11-5 in 35 minutes to become the second woman to win the title twice, after Malaysia's Nicol David.
"I'm one of the oldest on Tour and as long as I feel I'm still in contention to win titles, I'm happy," she said.
Compatriot James Willstrop was beaten 12-10 11-9 11-8 by Egypt's Mohamed Elshorbagy in the men's final.
Former world number one Willstrop, who is now ranked sixth, said: "To make the final was a great pleasure. I was loving every minute, apart from losing.
"Full credit to him, he stopped me playing so there are no complaints."

It has estimated that Â£5bn will have been spent in Britain's shops over the weekend, as millions of people stocked up on food, drink and presents.
The BRC says many shoppers waited until the last minute to pick up a bargain.
Meanwhile, several retailers are reportedly bringing their online sales forward to Christmas Eve.
High streets, shopping centres and supermarkets were reportedly packed with shoppers on the last few trading days before Christmas.
Many retailers have already started discounting products in advance of the traditional "Boxing Day" sales.
Saturday was expected to have been the busiest day of the year on the high street, with credit card company Visa Europe predicting more than 31 million transactions.
Richard Dodd, head of media and campaigns at the BRC, said: "People have left it very late this year because of their reluctance to spend.  They are holding out for bargains.
"It's been a very busy weekend which will be crucial to delivering a Christmas that is acceptable, rather than exceptional," he added.
Supermarket chain Sainsbury's said the hour between 12:00 and 13:00 GMT on Sunday was its busiest hour ever in terms of the number of customers served.
The company said it expected to sell 225,000 bottles of champagne, 56 million mince pies, 52 million Brussels sprouts and 6,500 tonnes of potatoes over the festive period.
Traders in London's West End had predicted that one million people would shop in the area during the three days leading to Christmas Eve, spending an estimated Â£100m.
At Brent Cross shopping centre in north London, centre manager Tom Nathan said the weekend would be their busiest period because schools had broken up late and Christmas Day was on a Tuesday.
Elsewhere, Bluewater shopping centre in Kent expected more than 275,000 shoppers to pass through in the days before Christmas Eve, while Birmingham's Bullring centre predicted it would welcome about 340,000 consumers.
Bullring general manager Tim Walley said: "This Christmas we essentially have an extra weekend of trading in comparison to December 2011, so we're expecting a bumper weekend."
But despite optimism in some quarters, the Local Government Association (LGA) said confidence on the high street remained low.
Its annual Christmas survey found that 84% of town centre managers said confidence among shoppers had either not improved or worsened compared to Christmas 2011.
A cold and wet start to the winter could also be taking its toll on the number of shoppers visiting town centres, the LGA concluded.
Just 0.9% of Wales' firefighters are non-white, official figures have shown.
[NEXT_CONCEPT]
England's Laura Massaro defeated world champion Nour El Sherbini to defend her Dubai World Series Finals title.
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Christmas sales figures are likely to be "acceptable" rather than "exceptional", the British Retail Consortium (BRC) has predicted.