"Mladenov is a coach who won the title in his previous spells at CSKA and we hope he'll continue to be as successful," CSKA's majority holder Dimitar Borisov told reporters. "Last time he won it by a 16-point margin."
Mladenov will replace Dimitar Penev, Bulgaria's coach of the century, who was released after CSKA's 2-0 loss at Chernomorets Burgas on Sunday - the team's first match after the domestic league's winter break.
Mladenov will become CSKA's third coach this season after Penev, who guided Bulgaria to fourth in the 1994 World Cup finals in the United States, replaced Milen Radukanov last October.
Penev will remain at the club and replace Borisov as chairman.
"From now on, I'll only be a shareholder in the club," said Borisov. "I'll remain focussed only on financial support. Coach Mladenov, chairman Penev and chief executive Ventsislav Zhivkov will be responsible for all sporting activities."
CSKA said Mladenov, who turns 55 next month, will be officially presented to the media on Tuesday.
In his first spell as CSKA coach, crowd favourite Mladenov won the league title in 2003.
His second stab at the job was also successful as he led the 31-times champions to another title in 2008 but left soon after that with the club running into financial difficulties and excluded from the Champions League.
Mladenov, capped 59 times by Bulgaria between 1978 and 1988, also won four league titles and two national cups as a CSKA player in the early 1980s.
Mladenov is known as "The executioner of Liverpool" in his native country as his two goals helped CSKA to a 2-0 win over the English club in the European Cup in 1982 and a place in the tournament's semi-finals.
The former Bulgarian league top scorer also coached Litex Lovech in the Bulgarian top flight as well as clubs in Portugal, Greece, Saudi Arabia and Egypt.
In 2000, Mladenov took over as Bulgaria coach but left a year later after failing to qualify for the 2002 World Cup finals.
He will make his return on Sunday when CSKA host relegation-threatened Kaliakra.
The Reds are third in the standings with 36 points from 16 matches, three points behind surprise leaders Ludogorets.
