The 33-year-old was paraded on the pitch by club president Massimo Ferrero alongside fellow new recruit Luis Muriel following the 1-1 draw with Palermo.
The Cameroonian had earlier taken his place in the stands to watch his new side, who were pegged back after Eder's sixth-minute opener.
Eto'o also posted a picture of himself wearing a Sampdoria training top on Twitter on Sunday morning, adding the message: "Successful medical. Thank you Dr Parfait Ondo. Ready for a new challenge!!!"
And the striker also appeared in a selfie alongside Ferrero and Muriel which was posted on Twitter by the club's official account.
