The fast-food giant said the nuggets, made from soy and plant proteins, had been certified by the Vegan Society.
Burger King previously released a plant-based Rebel Whopper burger two years ago, but it was later revealed to be unsuitable for vegans because it was cooked on the same grill as meat.
It has introduced a Vegan Royale burger as demand for such products has risen.
A vegan diet involves cutting out animal products such as meat, fish, dairy and eggs.
Burger King said its 50% meat-free target would help it reduce greenhouse gas emissions by 41%. It said its vegan nuggets would taste the same as its chicken-based counterparts.