The 28-year-old striker, who was on loan at Iraklis last season, has signed a two-year contract after Legia accepted a fee believed to be in the region of €70,000 for the player.
Mieciel was expecting to see out the remaining five months on his Legia contract after the Warsaw club rejected an initial Iraklis bid. However, the clubs struck a deal after a second round of talks, and this will involve a friendly match between them in the Polish capital with Legia taking all the proceeds.
Mieciel, who has scored one goal in five internationals, will join two other Polish arrivals at Iraklis - defender Miroslaw Sznaucner and forward Cezary Kucharski.
©UEFA.com 1998-2017. All rights reserved.