Forest habitats in Učka Nature Park are the most numerous, covering more than 70% of the total park area. The most strikingly distinctive feature of Učka and Ćićarija from the naturalist perspective is the occurrence of beech forest in peak areas above 800 m. These forests are not continuously connected to other beech forests in the littoral range of the Dinaric mountains, but tower like isolated islands above the sub-Mediterranean area. Most of the beech forests belong to the community of littoral beech forest association, which shows some distinctively transitional characteristics of the Mediterranean towards the continent; only the peak area of Mount Učka is overgrown with sub-Alpine beech forest.
The most important forests in the Mediterranean-montane vegetation zone are hop-hornbean forests with autumn moor grass and oaks.
Other, less-frequent forest associations include the sub-Mediterranean sweet chestnut forest on the eastern slopes of Mount Učka, and the downy oak and oriental hornbeam forest, which can be found today in the form of degraded thickets and stump forests in the warmest parts of the park.
Učka Nature Park also encompasses relatively large areas afforested with conifers, mainly black pine (Pinus nigra) and spruce (Picea abies).
Forests are home to many endangered and protected plant species, such as spurge laurel (Daphne laureola), dogtooth violet (Erythronium dens-canis), martagon lily (Lilium martagon), and many more. Despite the fact that all three mentioned species are rare and endangered, they are still often gathered by day-trippers.