The well-travelled former Tottenham and Middlesbrough striker has ended a third spell with his boyhood club, where he has fallen out of favour following a wage dispute.
The 29-year-old passed a medical at Oakwell on Thursday before completing the deal, allowing Barnsley to confirm their second signing of a productive week later today.
Mido told Sky Sports News: "I think everyone knows England has the best football in world and the best league.
"I have played in France, Holland, Italy and Spain and the best league for the way I play is England. I still have a lot of friends here.
"The Championship is a tough competition - harder than people think - but hopefully I can help.
"And with some new signings here we could have a good team. It will be hard work but we could do well and get ourselves in a good position in the table."
Former Chelsea youngster Jacob Mellis, who was infamously released by the UEFA Champions League winners after letting off a smoke grenade at their Cobham training ground in March, joined Keith Hill's men on a two-year deal on Tuesday, while winger Jim O'Brien signed a contract extension of the same length on Thursday.
"It's a great signing for the football club and for the profile of the club," Barnsley manager Keith Hill told the club's official website. "I am looking forward to working with a player of exceptional talent.
"There will be plenty of work to be done and that will be a reflection of what we will see on match day. We can't wait to get going."
Mido counts Ajax, Roma and Marseille among his former clubs but has been dogged by fitness issues over recent seasons and last played for his country in 2009.
During his last spell in England with Middlesbrough he spent time on loan with Wigan and West Ham.