Karacan, 33, has a wealth of experience across the globe, but may be remembered most fondly for the 155 appearances he made for Reading between 2007-2015.
He also boasts Champions League experience during his spell with Galatasaray, having made his competition debut by playing 90 minutes away at Atletico Madrid during the 2015/16 season.
Karacan was most recently at Scunthorpe United but left the club following the expiration of his contract at the end of the 2020-21 season.
He has already begun training with the Boro as they ramp up their pre-season preparations ahead of the Pitching In Northern Premier League season’s return.
“I’m looking forward to getting going,” Karacan said. “I’ve been fortunate enough to play at the highest level, and if I can bring a little bit of help, guidance and experience to the lads out on the pitch and help them perform better, that’s all I can do.
“It’s one of the reasons I came here. I want to give back to the younger lads and go on to achieve good things in the game.
“You can have all the ability in the world, but if you don’t give 110% every game you’re not going to get anywhere. I pride myself on giving that.
“I’m just hoping that I can bring that to the team and be a good person around the place.”
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