The 30-year-old winger has joined the A-League champions, in what coach Graham Arnold has described as a "major coup".
"He is a player I believe will add more of the x-factor to our front line," Arnold said.
"After speaking to Adrian, he ticked all the boxes with his character and I look forward to working with him."
Former Polonia Warsaw ace Mierzejewski was the Polish league's Player Of The Year in 2010.
His transfer to Turkish top flight side Trabzonspor in 2011 was reportedly for a record fee for a Polish league player at the time.
In 2012, he was a member of Poland's national team at the European Championships on home soil.
The 40-capped Poland midfielder has played in the UEFA Champions League and UEFA Europa League for Trabzonspor, and the AFC Champions League for Saudi Arabian club Al-Nassr.
"I'm extremely pleased to be joining the Hyundai A-League double winners and can't wait to begin the challenge of improving on last season," Mierzejewski said.
"There is a big challenge ahead of us with the added excitement of an AFC Champions League campaign."