Sinsheim - Former Belgium Under-21 international goalkeeper has left TSG 1899 Hoffenheim for VfL Wolfsburg on a three-and-a-half-year deal.
The 22-year-old has signed on the dotted line at the Volkswagen Arena until 30 June 2018, but will spend the second half of the current campaign on loan at fellow Bundesliga outfit SV Werder Bremen.
"In Casteels, we've signed a young, but also an experienced Bundesliga keeper, who will give our squad more depth in that position," explained Bremen sporting director Thomas Eichin. "Our undisputed No1 remains Raphael Wolf, who will be perfectly supported by him [Casteels] and Richard Strebinger." Casteels, who joined Hoffenheim from Belgian side KRC Genk in August 2011, hasn't featured in the Bundesliga since breaking his leg in the 1-1 draw with Hertha Berlin on 6 April 2014. He made 40 first-team appearances in all competitions for the Sinsheim club.