You can absolutely wear jeans in Croatia, as they are a staple of the local casual and "smart-casual" fashion scene. Croatians are generally quite stylish and tend to follow European fashion trends, so a pair of well-fitted, clean jeans is perfectly acceptable for sightseeing, dining in "konobas" (local taverns), and traveling between islands. However, there are two important considerations. First, the weather: during the peak summer months (July and August), the Mediterranean heat and high humidity can make heavy denim extremely uncomfortable; locals typically switch to light linen or cotton trousers during the day. Second, the context: if you are visiting religious sites like the Cathedral of St. James in Šibenik or monasteries in Dubrovnik, you should ensure your attire is respectful; while jeans are usually fine, they should not be overly distressed or ripped. For evening drinks at a chic Hvar beach club or a high-end restaurant in Zagreb, you might want to pair your jeans with a nice blazer or blouse to match the "effortlessly polished" vibe that many Croatians prefer.