The minimum became mandatory for all newly signed contracts from August 30, and will now also be compulsory for existing employment agreements.
It requires that all workers, including domestic staff, be paid at least 1,000 riyals ($275) for a month of full-time work - equivalent to around $1.30 an hour.
Employers are also required to either provide bed and board, or an additional 800 riyal a month allowance for food and accommodation.
Previously, there was a temporary minimum wage set at 750 riyals ($206) a month.
The state-run Qatar News Agency reported that the labour ministry had "announced implementation of new minimum wage for all workers starting Saturday".
Campaign group Migrant Rights has said that the new level is too low and does not reflect Qatar's high cost of living.
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The labour ministry has said the changes will "boost investment in the local economy and drive economic growth".
"Qatar is the first country in the region to introduce a non-discriminatory minimum wage, which is part of a series of historical reforms of the country's labour laws," the International Labour Organization said in a statement.
"More than 400,000 workers or 20 percent of the private sector will benefit directly."
Qatar has made a series of reforms to its employment regulations since being selected to host the 2022 World Cup, which has required a vast programme of construction dependent on foreign workers.
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