Veteran midfielder Costinha has left Atalanta after his contract was terminated by mutual consent.
The former Portugal international joined the Serie A club from Atletico Madrid in the summer of 2007.
But he has rarely featured in recent times and an agreement has been reached for the 35-year-old to be released.
Costinha is now a free agent but it remains to be seen whether he will seek another challenge in his playing career or hang up his boots.
Atalanta are currently languishing in the relegation zone and face a battle to secure their top-flight survival.