Milojevic, who was seeded No.1 before clinching the title, beat Canada's Tommy Mylnikov in the final Monday to win the bowl's 150 points, reports Xinhua.
The Costa Rican competition is considered the second-most important junior (Under-18) tennis tournament in the world by the International Tennis Federation (ITF), after the "junior Grand Slam."
In the women's category, Russia's Varvara Fink beat her rival 2-6, 7-6(2), 6-2 to become only the second Russian ever to win the bowl.
Fink's win was a surprise upset as she entered the tournament seeded sixth but went on to defeat higher-ranked competitors.
Croatia's Franko Miocic and Chile's Guillermo Nunez won the men's doubles title while the women's doubles was won by Mexico's Alejandra Cisneros and Victoria Rodriguez.
The Coffee Cup showcases the best young talent in the world with many of its winners turning pro such as Guillermo Vilas, Ivan Lendl and the Swiss maestro Roger Federer, as well as Andrea Holikova, Jana Novotna and Sandra Wasserman.
