Mladen Pralija was born on January 28, 1959, in Šibenik, Yugoslavia. He started his professional soccer career with Hajduk Split. He also played for RNK Split and Šibenik in the Yugoslavian League.
In the 1987-88 season he played for Hamburger Sport-Verein in the German Bundesliga. After one season with the German club he joined Croatian League club Čelik Zenica. He then returned to his former club Hajduk Split.
Mladen joined Toronto Croatia before the start of the 1992 National Soccer League season. He helped his club win the 1992 league championship.
In the 1993 Canadian National Soccer League season Mladen finished the regular season as the leading goalkeeper. He played in 16 league games and let in 10 goals, having a Goals Against Average of 0.60.
Mladen later became a coach.