One of the best hotels on the island is the Grand Hyatt Kaua'i. That being said, it has some of the best restaurants on the island too. Tidepools is located on the pools of the resort with cute thatched hut-style roofs. Their menu has vegetable samosa and the garden isle salad for starters. For your main meal, they have tofu hiryozu which is quite tasty. It is like tofu crab cakes almost. Also located at the hotel is Yum Cha, an asian eatery. To begin, one can get their wok seared edamame. Their miso soup has fish broth in it, but they made me a vegan version special when I asked if it did have it in it. They also made me tofu summer rolls. For dinner, we had stir fried wild rice and stir fried seasonal vegetables. Overall, it was an excellent meal and the service was incredible. They went above and beyond to please us and had very generous portions for the price.
Another south shore favorite is Keoki's Paradise. While this is primarily a fish place, they do have some veggie options. For starters, one can have their house salad and for dinner, they have a teriyaki stir fry with vegetables and rice. For lunch, they have grilled veggie sandwich (get it without cheese and aioli).
A classic plantation in Kaua'i is Kilohana. It is a must see for its rustic beauty. The restaurant at the plantation used to be called Gaylord's but in the last year and a half they have changed it to 22 North. They pride themselves on farm raised food and local vegetables. Their menu changes from week to week. 22 North was very accommodating to vegetarians and vegans. I had herb roasted macadamia nuts, the estate salad (garden salad), a couscous stuffed tomato with crispy kale and zucchini, and ended it all with coconut sorbet. The restaurant is located facing out over the plantation with a lovely Hawaiian atmosphere.
Roy's is a world famous Hawaiian fusion restaurant with many Japanese influences. They even have a location here in Chicago. The one in Poipu had a small separate vegetarian menu. To begin, I had a tofu and mushroom appetizer and a garden salad. For my dinner, I had a vegetable stir fry with rice and then for dessert, fruit sorbet. They also serve sesame oil edamame instead of bread. Overall, Roy's is a fun place to go for a nice dinner.
On the east side in Kapa'a, there is a small lunch and dinner spot called Mermaid's Cafe. They have a really vegan-friendly menu and it's cheap. They serve a tofu satay plate, tofu curry plate, tofu stir fry noodle plate, tofu satay wrap, organic salad, and a black bean burrito (no cheese). Basically, the whole menu can be made vegan. Also in Kapa'a is Sukhothai Restaurant, a great Thai restaurant that is very good. Another Thai place in Kapa'a is Mema Thai. Other Asian restaurants in this city are Sushi Bushido and Shivalik Indian restaurant. A great kaiten sushi (sushi served on a conveyor belt) joint in Lihue is Genki Sushi. It's cheap and tasty!
Lastly, I went to Merriman's Restaurant which is located in Poipu. The waitress there was also vegan and helped me out with their menu. If you are reading this, thank you! I really appreciated it. She also has a vegan baking business called Hippie Cafe Kaua'i. Check it out! She recommended a restaurant called Caffe Coco in Wailua which is vegan-friendly. At Merriman's I had the petite lettuce salad to start and for dinner, I had the veggie platter. The veggie platter had lovely moist taro cakes and fresh crunchy green beans. Just don't get the honey sour cream on it.
Well, that is everything I have to say about vegan-friendly places in Kaua'i. I hope someone finds this helpful and enjoys this beautiful island as much as I do.