Maaloul, who turns 56 later this month, takes over from Djamel Belmadi, who quit and is widely expected to be appointed coach of the Algerian national team.
The club added that Maaloul was already on his way to Austria to meet players at a pre-season training camp.
The Tunisian football federation announced earlier they had agreed to a request from Maaloul to end his contract following an offer from Al Duhail.
Maaloul had been in charge of the national side since April 2017.
They were formerly known as Lekhwiya but last season the club was merged with El Jaish to form Al Duhail.
Maaloul was the coach of El Jaish, back in 2014.
Qatar's domestic season starts on August 4.
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