Papadopulos started his football career in his native Ostrava at NH Ostrava, and then Baník Ostrava. He moved early to English club Arsenal in July 2003. He played just one first-team match for Arsenal, in a League Cup match against Wolverhampton Wanderers as a substitute for Jérémie Aliadière. He returned to Baník in 2004. Papadopulos won the Czech Cup with Baník in 2005. In December 2005, he moved to Bayer Leverkusen, spending some time on loan at German side Energie Cottbus before signing with Czech side Mladá Boleslav in June 2008. In June 2009, SC Heerenveen signed the Czech forward from Mladá Boleslav on a five-year contract.