On 9 June 2010, he signed his 3-year contract. On 30 June 2010, he made his unofficial debut for Levski in a match against FCM Târgu Mureş. Mladenov entered the match as a substitute and scored 2 goals.
Mladenov officially debuted for Levski in a Europa League match against Dundalk F.C. The Blues won the first match and the result was 6:0. Mladenov scored two of the goals.
On 16 December 2010, Mladenov netted the only goal (right at the end of the first half) for Levski Sofia in the 1:0 home win against Sporting CP in the final UEFA Europa League match of the group phase. However, the team from Sofia had already been eliminated from the competition.
Chernomorets Burgas
On 3 August 2012, he signed a 2-year contract with Chernomorets Burgas for free.[1] On 13 December, he was arrested for illegal betting.[2] Three days later he was released from the club.[3] However, he did not face any legal charges.
PFC Montana
In February 2013, Montana acquired the services of Mladenov until the end of the 2012/13 A PFG season.[4] At the end of season his contract had expired.