Mladenov's finest game as a player was on 17 March 1982, when he scored both of CSKA's goals as they beat Liverpool 2–0 in Sofia to knock the English giants out of the European Cup quarter-finals.

Financial problems at his favourite club CSKA Sofia pushed him away after a series of compromises he had done during his time there.

He was recently fired as manager of Al-Ettifaq FC after the team failed to win in 4 consecutive games.

In his initial stint at CSKA Sofia (between 2002 and 2003), Mladenov led the team to its first A PFG title in 6 years.

In March 2012, he replaced Dimitar Penev as head coach of CSKA Sofia and led the team to a second-place finish during the 2011/2012 A PFG season.

[2] He resigned in March 2015 despite the successful season for the team, which was able to pose a challenge to Ludogorets Razgrad for the title.