Born in Porto Alegre, Rio Grande do Sul, Cássio was signed by RS Futebol in December 2004 along with his twin brother Rafael.

[1] Cássio made his Brazilian Série A debut on 26 October 2006.

In June 2007 he was loaned to Avaí in 2-year deal, which Rafael already arrived in March.

Traffic Group then loaned him to Série A side Fluminense, another club partner, in 2-year deal.

In February 2011 he returned to Avaí in 2-year deal[3][4] as his twin brother transferred to Europe.