KFC has said it will sign up to the Broiler Ask –also known as the Better Chicken Commitment – by 2026.
It joins more than 30 companies in Europe signed up to the measure, including M&S, Waitrose, Unilever and Nestle.
KFC is arguably the highest-profile signatory to date in the UK that is not a premium-tier retailer.
Compassion in World Farming said it would improve the lives of 72 million chickens a year –about 4% of the UK flock.
Paula MacKenzie, CEO of KFC UK & Ireland, said: “Our business depends on the health, sustainability and reputation of chicken farming, and our customers care about improving the lives of the chicken we buy.”