The Doha-based club announced the signing on Twitter, saying the 37-year-old would be unveiled later on Tuesday.
Eto'o, a four-time African footballer of the year, becomes the latest big-name arrival to join the Qatar Stars League after ex-Spain international Xavi and former Netherlands playmaker Wesley Sneijder.
Africa Cup of Nations
Cameroon progress at Africa Cup of Nations as Aboubakar eyes Eto'o records
He played with Xavi at Barcelona and Sneijder at Inter Milan, winning the Champions League with both teams.
Eto'o is Cameroon's all-time leading goalscorer with 56 goals, and twice an African Cup of Nations winner.
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Spanish Super Cup
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