The 30-year oldâ€™s previous contract was set to expire at the end of the season but the Reds have moved to secure him until the end of the 2012/13 season.
There was speculation surrounding the former Flamengo and Santa Cruz manâ€™s future at Hindmarsh Stadium but that has been settled by this latest announcement which has delighted the player himself.
â€śI feel very good and very happy with this deal. My decision wasnâ€™t so hard because since I arrived here I have felt at home,â€ť Cassio said.
â€śThe supporters, the club, my teammates, the new owners and the Adelaide people made my decision easy with how they have treated me, so thatâ€™s why I chose to stay here.â€ť
Cassio, who joined the Reds in 2007, said he was currently feeling in the best shape of his career.
â€śIâ€™m 30 years old at the moment and to be honest I feel much better physically than when I was 20. Donâ€™t ask me why, but I feel more confident, and after you get experience, you know where to run and you get smarter,â€ť he added.
â€śFootball is my life and I know I have to keep performing well, playing good and giving Adelaide my best. This season has been great for me and I hope the next two can be even better.â€ť