Yorke confirmed his departure from Stoke earlier this week after four seasons with the Knights, during which the prop played 78 times and scored 18 tries.
The 26-year-old has become York’s second player to move to London from the Betfred Championship club until 2023, following the signing of Sam Davies.
Stoke said: “London was always my local team to follow growing up and I wanted to explore moving south to play and be closer to friends and family.
“This is a great opportunity for me and playing for the Broncos was a real goal of mine when I was younger.
“I’m looking forward to working with Mike (Eccles, director of rugby and performance) and his coaching team and doing the pre-season strength and conditioning sessions I’ve heard so much about.
“I am familiar with several individuals in the team. Sam and I get along well, and there are a few other mutual contacts that will make the transition from one team to another easier.”