It will be Östers Robin Wallinder who will replace Noel Törnqvist who is moving to Italian Como.
"Robin has impressed with his efforts for Öster and has been considered by many to be one of the best goalkeepers in the Allsvenskan this year," says Mjällby's sports director Hasse Larsson to the club's website.
Wallinder, 26, has played 64 games for Öster and has previously played in Gefle, Örgryte and Ljungskile, among others.
He was involved in bringing Öster up to the Allsvenskan a year ago and was now involved when the Växjö team went down to the Super League again.
