Burger King, the world's second largest burger chain, is to increase supplies of humanely-sourced meat and eggs.
Burger King says 2% of its eggs will be from non-caged firms
Animal rights groups, including People for the Ethical Treatment of Animals (PETA) - a critic of the farming behind fast-food - have praised the move.
The decision to encourage the use of cage-free chickens and free-range pigs will apply to the US and Canada.
Burger King aims to source 2% of eggs from non-caged birds and 10% of pork from pigs allowed to roam freely.
Burger King has told its suppliers that if they provide eggs from caged-free hens they will get a better deal.
The firm said it hoped to expand the market for such eggs.
"The fact that Burger King has made positive changes for some of the animals killed for its restaurants will send a ripple effect through the fast food industry," said PETA spokesman Matt Prescott.
It would show other companies that animal welfare "cannot be ignored," he said.
"Suppliers will hopefully respond by producing more of these types of products," Mr Prescott added.
Burger King said it would also prioritise products from suppliers using controlled stunning as the way to kill birds.
Animal rights groups have criticised other methods, such as gassing.
In February, UK supermarket chain Sainsbury's promised to cease selling battery eggs by 2012.
By then, 100% of its 600 million eggs sold annually will be either free-range or barn eggs laid by hens allowed access to natural light.