New Town head coach Jan Siewert previously worked with Winkler at Rot-Weiss Essen and wants his compatriot to be his No 2 at the John Smith’s Stadium.
Winkler was sporting director during Siewert’s spell as head coach at the Stadion Essen from June 2015 to April 2016.
The pair originally both became friends while completing coaching qualifications together ahead of Siewert being approached by the German Football Association to become their Under-17’s coach.
Siewert later renewed acquaintances with Winkler at Essen when he became the youngest head coach at the club in almost 40 years.
Meanwhile, young Barnsley midfielder Romal Palmer has extended his loan at National League North side Darlington for the rest of the season.
Palmer, 20, impressed in a youth loan spell with the Quakers late last year.
Bradford City have turned their attentions towards landing further targets following their signing of Preston full-back Calum Woods.
The former Huddersfield Town defender, 31, has initially signed a permanent deal until the end of the season.
Woods becomes Bradford’s third addition of the January transfer window following the earlier captures of Peterborough United midfielder Jermaine Anderson and Leeds United loan defender Paudie O’Connor.
The Scot, keen to kickstart his season after an injury-hit time at Deepdale, said: “As soon as I knew Bradford were interested, I wanted to come and play.
“I have played in this league before, as well as having enjoyed a few promotions into the Championship, so will bring some experience with me.
“Bradford is a massive club and everybody knows that,” he added.
“We are not where we want to be at the minute but, hopefully, we can start to push ourselves up the table.
Bantams manager David Hopkin added: “We are delighted to have got this deal over the line.
“It is one, along with several others, we have been working on for some time now.
“Calum will bring a wealth of experience to the squad and add competition for places at the back.”
Swedish defender Thomas Isherwood has left the club by mutual consent.