In addition to Heineken brands, visitors will also be able to taste local craft beers.
The festival, which will also include gastronomic and entertainment programmes, will last until Tuesday.
This year marks the 170th anniversary of the Karovačko beer, the signature product of the Karlovačka Pivovara bewery, a Heineken International subsidiary, and the 40th anniversary of the Karlovac festival.
Free parking zones and free bus lines connecting the city centre with the festival venue have been introduced for the duration of the festival, as have discounted train tickets for visitors coming from Zagreb.