Mladenov's nickname is "Liverpool's Executor" in honor of his winning goals against the European champion Liverpool FC in UEFA European Champions Cup 1/4 finals in season 81/82.
Mladenov played also in Portugal in several clubs like V.Setúbal,GD Estoril-Praia, Olhanense, but was in C.F. Os Belenenses where he achieved one third place in Portuguese football league and won a Portuguese Cup beatting Benfica in the final, after winning in the prior stages teams like FC Porto and Sporting CP.
He was also responsible for the victory that Belenenses had over Barcelona in the UEFA Cup of 1988 , when he stole the ball from Barcelona's defender Shuster and made a perfect assistance for Mapuata's goal. Nowadays he trains the most successful Bulgarian team CSKA Sofia. Finacial problems at his favourite club CSKA Sofia pushed him away after a series of compromises he had done during his time there. Now he is a coach at Al-Ahli. His son Alexandar Mladenov is a professional footballer.