Thestrals are purely carnivores, meaning that they eat meat. Thestrals have been known to chase and devour even large species of bird. They also eat other creatures such as rabbits, rats, lizards, fish, and even deer.

Thestrals are incredible predators, able to take down prey items much bigger than themselves. Some Thestrals will charge their prey to stun them before finishing the job with their bone-crushing, beak-like mouths. A Thestral will chase its prey for miles before tiring, and their incredible speed makes it easy for them to take out prey quickly.

Thestrals are also scavengers. They will take advantage of any opportunity given to them, including rotting carcasses. Due to other habits in their diet, Thestrals are able to eat spoiled meat to sustain themselves. Thestrals prefer to hunt and eat fresh meat, though, and only scavenge in dire situations.

A Thestral eats every piece of the animal it kills besides the bones. Although the structure of their mouths allows them to crush bone with ease, their stomachs are unable to digest bone matter. This is why it is common to find bone remnants scattered around a Thestral's territory.

Crushed rocks are a common part of a Thestral's diet as well. They use the rocks to ease their stomachs if they are upset. The stone helps reduce the acidic reactions in their stomach and makes digesting rotting prey easier.