Mladenov also holds the record for the most professional international doubles titles in Bulgarian tennis history (18 ITF titles) Mladenov also played for two years at the number 1 position at St. John's University (New York) in ITA Division 1.

He participated in the Davis Cup in doubles in March 2016 against Turkey, bringing Bulgaria a historic win 7:6, 6:7, 6:7, 7:6, 6:4 alongside fellow Bulgarian Alexander Lazov.

When he was five he began to play with his grandfather, Lev Shulga, who is a well known coach from the former U.S.S.R. Vasko speaks fluent Bulgarian, Russian and English.

In 2021, as a public figure, Mladenov took part in the second season of the Ukrainian version of “The Bachelorette” («Холостячка»), a famous romantic TV reality show, which ended up being the most watched TV show in Ukraine that year.

Alongside his partner Kiril Dimitrov (BUL) he achieved a total of 5 international tournament titles between 2021 and 2023.

Vasko Mladenov debuted for the Bulgaria Davis Cup team in 2016 against Turkey in Ankara.

He participated in Davis Cup in doubles in March 2016 against Turkey, bringing Bulgaria a historic win 7:6, 6:7, 6:7, 7:6, 6:4 alongside fellow Bulgarian Alexander Lazov.