Adamczyk joined Chelsea in the summer of 2014 and has now returned to Poland after an unsuccessful spell at Stamford Bridge.
The 17-year-old signed a professional contract with the Blues seven months ago, but the lack of progress and slim chances of making it to the first team have forced him to consider a move away.
The talented attacking midfielder is keen to play regularly and Chelsea have decided to cut their losses on Adamczyk. The player has been unveiled at MKS Cracovia and the reported fee is believed to be in the region of £76,500.