Tofu is commonly used as a vegetarian substitute in Pad Thai.
Firm tofu is cut into small pieces or strips and stir-fried with rice noodles, eggs, bean sprouts, and the sweet-sour sauce. It provides protein and a pleasantly chewy texture while absorbing the flavors of tamarind, fish sauce, sugar, garlic, and shallots. Traditional versions may also include dried shrimp or fresh shrimp, so tofu does not automatically make every Pad Thai vegetarian.
Vegetarian and vegan versions usually omit shrimp and fish sauce as well as meat. Cooks commonly replace fish sauce with soy sauce, tamari, or another plant-based seasoning. This is an important distinction: tofu itself is vegetarian, but the surrounding sauce and condiments may contain seafood ingredients.
Tofu is not the only possible substitute. Tempeh, seitan, mushrooms, or additional vegetables can also be used in modern recipes, but tofu is the familiar and widely recognized choice associated with vegetarian Pad Thai. Paneer is less typical because it belongs to South Asian cuisines and does not commonly appear in Thai Pad Thai.