Cats can eat parsley in moderation, and it can even provide some health benefits due to its rich content of vitamins A, C, K, and antioxidants. Parsley may help support immune health, promote healthy blood clotting, and aid urinary health. However, caution is advised because large amounts of parsley — especially certain types like spring parsley and curly parsley — can be toxic to cats. Excessive consumption can cause photosensitization (making the skin sensitive to sunlight), and parsley can act as a diuretic, so it should be given sparingly. Parsley water is often recommended as a safer way to offer parsley benefits to cats. It is important never to feed cats large amounts or certain toxic varieties, and always consult a veterinarian before adding parsley regularly to a cat's diet.