Yes, wearing jeans is perfectly acceptable on almost all modern cruise lines, but there are a few "unspoken rules" regarding when and where you wear them. During the day, casual denim is the norm for exploring the ship or going on shore excursions. For evening dinners, most "Main Dining Rooms" allow jeans as long as they are "dressy"—meaning no holes, fraying, or excessive bagging. On "Smart Casual" nights, pairing dark-wash jeans with a nice blouse or a collared shirt is a common and stylish choice. However, on "Formal" or "Elegant" nights, many cruise lines (especially premium ones like Cunard or Celebrity) still encourage guests to opt for slacks or suits, and some may even restrict denim in the most upscale specialty restaurants. If you prefer to stay in your jeans all night, the buffet and casual poolside grills never have a dress code, ensuring you can still enjoy your vacation without ever putting on a tie or a gown.