Blatter said that the technical report into Qatar's bid had warned that it was too hot but despite that, FIFA's executive committee had voted for the Middle Eastern country.
The FIFA president said it was now "probable" that it would be played in the winter rather than the summer due to the heat.
Blatter told Swiss TV station RTS: "Yes, it was a mistake of course, but one makes lots of mistakes in life.
"The technical report into Qatar said clearly it was too hot but the executive committee - with a large majority - decided all the same to play it in Qatar."
There have also been numerous corruption allegations about the bidding process for the tournament and reports of alleged abuses of the rights of migrant workers employed on World Cup projects.
Blatter insisted however that Qatar had not "bought" the World Cup - the bid did spend large amounts of money on sponsorship and development programmes.
He added: "No, I have never said it was bought, but that it was due to political considerations."
A report in the Daily Mirror in March claimed that over a thousand people have died in Qatar during their £39 billion building spree for the 2022 World Cup.
In a Special Report for Eurosport last September, Philippe Auclair exposed the unseen human cost of holding the World Cup in Qatar.
"Qatar can boast of the highest GDP per capita in the world - $106,000 (£68,000) in 2012, according to the International Monetary Fund. But this figure doesn’t reflect the huge disparity between the incomes of Qatari nationals and the non-national transients who make the overwhelming majority of the population, and whose lot is a sorry one," wrote Auclair.
"The recruitment process itself is highly suspect, relying on a system of sponsorship via placement agencies which is widely abused; passports may be confiscated on arrival; and, once in situ, those immigrants are routinely denied basic rights granted to workers in most parts of the world. They are de facto non-citizens. Football has, so far, chosen to ignore this.
"According to all independent reports, those migrant workers toil six days a week (no summer break for them), 10 hours a day, for less than $10 (£6.40) a shift. They are crammed in rudimentary camps mostly devoid of decent sanitation and – not a luxury in Qatar – air conditioning.
"Though official statistics are not available, credible evidence has emerged to suggest a staggering death rate among the young, fit men who come to work there."
In March, Qatar's 2022 World Cup organising committee were forced to come out and deny being aware of any alleged payments by the disgraced former head of the country's football association to an ex-vice president of FIFA.
Britain's Daily Telegraph newspaper reported that a company under the control of Mohamed Bin Hammam paid $1.2 million to Jack Warner, the former president of North American football's governing body CONCACAF and a member of the FIFA committee which chose the 2022 World Cup hosts.
- Sports & Recreation
- 2022 World Cup