The 34-year-old announced his retirement on the 27th August after his contract with Juventus was terminated but after Barcelona lost key player Marc-Andre ter Stegen due to a serious knee injury last month he changed his mind.
Szczesny made 181 appearances for Arsenal and over 270 appearances in the Serie A for top sides such as Juventus and Roma, winning three Serie A titles and three Coppas Italia.
The Polish international announced his retirement after stating that he is not mentally up for football anymore on a post to his fans on Instagram.
"Today, though my body still feels ready for challenges, my heart is not there any more. I feel that right now it is time to give all of my attention to my family."
On Tuesday night Hansi Flick's side beat Young Boys 5-0 in the Champions League as Inaki Pena started in goal. Szczesny could get his chance against Deportivo Alaves at the weekend as the Catalonian club look to remain at the top of the table.