The London club's decision to dismiss Jerry Quy, who played the role for 27 years, inspired fundraisers and an offer from Gunners midfielder Mesut Ozil to pay his wages.
On Tuesday the character's Twitter account posted a photo saying: "Back at the Emirates Stadium today".
It is uncertain who is playing Gunnersaurus in the image, but reports suggested there was a roster of people now playing the part of the dinosaur and that the club had offered Quy a role.
"As we've always said, Gunnersaurus is an important part of Arsenal and a popular figure for our fans around the world," said a club spokesman.
"Gunner never went away but due to the virus restrictions there have been limited opportunities for him to appear in public."
The Twitter post received over 40,000 likes in less than an hour, with supporters, currently shut out of Arsenal's Emirates Stadium due to coronavirus restrictions, relieved to see him back.
Fans had used a GoFundMe page titled "Save Gunnersaurus" to raise nearly £12,000 ($16,000).
A statement on the page reads: "Gunnersaurus has been the Arsenal club mascot for 27 years. He's a club icon and we cannot let him become extinct."
Ozil, who reportedly earns £350,000-a-week, offered to pay for the "famous and loyal mascot" to continue as long as he plays for the Premier League club.