Mourinho, who was also Eto'o's manager at Inter Milan, was caught on camera making unguarded comments suggesting the Cameroon striker was older than his official age earlier this season.
The 33-year-old, in line to feature in his fourth World Cup this summer, responded by celebrating his next Chelsea goal as if he was a geriatric.
Now Eto'o, who is out of contract this summer after scoring 12 Chelsea goals, plans to continue to ply his trade in one of Europe's top leagues.
Eto'o told africanfootball.com: "Thanks for informing me that it will be my last World Cup.
"Today, I am 33 years old. And it is not because a fool called me an old man that you must believe it.
"And you may have noticed that the old man was better than the youngsters.
"Some believe I am going to retire in the United States or in the Middle East, but I have regained the joy of the Champions League and I am going to carry on playing in the Champions League. Where? I am not going to tell you.
"But I am going to carry on playing because physically and mentally I feel great.
"So I am going to go to this World Cup and to the next one when I will be 37.
"Some did it at 42, so I can still play in two more World Cups."
Following Chelsea's final game of the season at Cardiff, Mourinho suggested Eto'o would depart this summer, at the end of his one-season deal.
The Chelsea boss will wait until pre-season before determining the futures of his loan stars.
Mourinho presented his end-of-season report to the Chelsea hierarchy on Monday, detailing his thoughts on all matters relating to the first-team squad.
Definitive decisions on goalkeeper Thibaut Courtois, striker Romelu Lukaku and the others who spent time away from Chelsea this season will wait until after training resumes on July 8.
Courtois has impressed in his third consecutive season on loan at Atletico Madrid, helping the Spaniards to the May 24 Champions League final at the expense of his parent club, and could put pressure on Petr Cech as Chelsea number one.
Lukaku spent a second straight season on loan in the Premier League, scoring 17 goals for Everton - a tally greater than any of the strikers who remained at Stamford Bridge.
Others will also be looked at closely by Mourinho, including Victor Moses, who spent the season at Liverpool, and Marko Marin, who helped Sevilla to win the Europa League.
After Chelsea's final home game of the season, Mourinho insisted there was no rush to make decisions relating to his squad.
Tellingly, though, captain John Terry signed a one-year contract extension 24 hours after Mourinho's report was submitted.
The fates of record goalscorer Frank Lampard and left-back Ashley Cole are still to be clarified, with their contracts expiring imminently.