Each year, mid-October, Kostajnica commemorates the chestnut sativa days with rich cultural program and entertaining touristic activities. The Kestenijada event which has been taking place in Kostajnica ever since 1998 has the touristic, cultural and economic significance. The area of Kostajnica is rife with the chestnut sativa woods which was the main idea that inspired this event to be organized in the first place.

Kestenijada event lasts for three days, and the program encompasses numerous different activities such as:
- Ethno exhibition of women’s handmade works
- Elementary school students' art exhibition on the topic of chestnut
- Pre-school attenders' works exhibition
- Folklore dancing and singing groups performances
- Sales expo of souvenirs, fruit and honey
- Chestnut-ball – the costumed student's parade in chestnut and fall fruits creations, and the students' program for the Prince and the Princess of Kestenijada pageant, the most beautiful basket, hat and necklace
- Kestenijada Kotlić – contest of preparing local cuisine campfire pot stew
- Degustation of Kostajnica’s traditional dishes
- Roasting and degustation of chestnut in the town’s streets

During the Kestenijada event the scent of roasted chestnut spreads throughout the streets of Kostajnica, and all thanks to local people who roast the chestnuts and then give it away to all the visitors. Sunday is the day when the main part of the event takes place, and that’s when the visitors can not only to try roasted chestnuts, but they can also taste the traditional dishes from the area of Kostajnica, as well as the culinary specialties that the contestants of Kestenijada Kotlić (stew) prepare. Spending some quality time with local people along with singing and dancing are the key parts of what makes Kestenijada what it is, and mandolin musicians are there to additionally bright up the mood.