The centre-back joined Wednesday in 2018 and was an integral part of their run to the Championship play-off semi-final in his first season.
He made 42 appearances during his initial stint with the Owls and scored five goals, including strikes against Aston Villa, Wigan Athletic and Leeds United. His return is sure to bolster the team's defence this season.
Manager Tony Pulis said: “Aden is a leader and I’m pleased we have him back here with us now." "He brings experience and a wealth of quality which will be invaluable for our future plans," he added.
The 30-year-old has signed a two-and-a-half year deal with Wednesday, effectively keeping him at S6 until the end of 2022/23 season. He will wear the number 6 shirt for his second spell at Hillsborough.
Chief Executive Paul Bell said: “It is really pleasing to re-welcome Aden back into the fold. He enjoyed an excellent first season with us before joining Cardiff on loan last summer." "We look forward to seeing what he can bring over the next couple of seasons as part of our journey," Bell concluded.