What is the main sweetener in Pad Thai sauce?

The main sweetener in Pad Thai sauce is palm sugar. It contributes a rounded, caramel-like sweetness that balances the salty fish sauce and sharp tamarind in the dish's characteristic sweet-sour-savory profile.

Palm sugar is made from the sap of palm trees and is widely used in Thai cooking. Depending on the region and recipe, cooks may use sugar from the palmyra palm or coconut palm; recipes may also call for ordinary granulated sugar or a mixture of sugars. These variations do not change the classic answer to this ingredient question.

Pad Thai became strongly associated with Thailand in the mid-20th century, although rice-noodle cookery had earlier Chinese influences. Its sauce is not simply sweet: tamarind supplies acidity, fish sauce adds salt and umami, and chili or lime may sharpen the finished dish. Brown sugar is a possible substitute, but it is not the traditional defining sweetener.