The vastly experienced striker has been without a club since leaving Chelsea at the end of June following the end of a one-year deal.
Everton manager Roberto Martinez has won out over a host of rival clubs to secure the services of the 33-year-old, paving the way for Eto'o to potentially face his former club at Goodison Park on Saturday.
The former Mallorca, Barcelona and Inter striker has scored over 250 goals in a club career that has seen him win both the Champions League and La Liga three times as well as Serie A, the Coppa Italia, Club World Cup and Copa del Rey.
Eto'o – who had been linked with Liverpool before the Anfield club signed Mario Balotelli from AC Milan on Monday - scored nine goals in 21 Premier League appearances for Chelsea last season and will bolster an Everton attack that includes club-record signing Romelu Lukaku.
Ajax also held talks with Eto'o but he has opted to remain in England.