Kraljevica is a small town and almost everything is walkable. The old town, both castles, the harbour, and the Oštro peninsula are all reachable on foot within 20–30 minutes of the centre. There is no need for local transport within the town itself.
For day trips, a car is strongly recommended. Buses connect to Rijeka and down the coast to Crikvenica, but frequency is limited and the island of Krk (while just across the bridge) is difficult to explore properly without your own transport.
The D8 coastal road through town can be slow in summer due to lorries heading for the Krk Bridge. The waterfront promenade is pedestrianised near the marina.