Djourou was reported to have passed a medical with Sheffield Wednesday.
A statement on the club's website confirmed Djourou has signed a contract for "2 + 1 years" at New Antalya Stadium, after leaving Hamburg in June.
Fans of the Owls, who have begun the season with only two recognised central defenders, were given fresh hope on Sunday, when The Sun reported they were ready to splash out to meet Djourou's contract demands - three years and £30,000 a week, allegedly.
But with three and a half weeks left of the summer transfer window, Wednesday will now have to look elsewhere for reinforcements.
Switzerland defender Johan Djourou
And finding a Djourou alternative may not be easy after Carvalhal told BBC Radio Sheffield last week that the Owls are 'on the line' in relation to the Football League's financial fair play restrictions.
Antalyaspor finished fifth last season and are captained by former Real Madrid and Barcelona striker, Samuel Eto'o.
Where should Sheffield Wednesday turn after missing out on Djourou?