The home support unveiled a banner with a message for the ex-Hibs striker who is taking time away from football to deal with “ongoing issues”.
Griffiths spent two seasons with his boyhood club, scoring 39 goals in 78 appearances.
The banner read: “Stay strong Sparky”.
Celtic boss Brendan Rodgers confirmed on Wednesday that the Scottish international will be unavailable for an indefinite period as he seeks professional help.
The news prompted messages of support for the Scotland striker from around football.
Griffiths said: “I just wanted to thank everyone at the club and so many Celtic fans and other people who have sent me such kind and powerful messages of support.
“I thank you all sincerely and want to let you know I’m doing all I can to come back as soon as possible, a better and stronger person.”
Join our Facebook group Our Edinburgh to share images and news from and around the Capital