Michael Hector will join Fulham from Chelsea in January on a two-and-a-half year deal.
The London clubs have agreed an undisclosed fee for the 27-year-old defender, with the Cottagers holding an option to extend his stay for a further 12 months.
The former Reading centre-back, who spent last season on loan at Sheffield Wednesday, will train with his new team-mates until he is free to play.
Hector told Fulham's website: "It was an easy decision to make. My Mum is from Fulham, so it's nice to join a club that some of my family support.
"It's good to now be a part of the set-up here. Hopefully things can work out well and we can get promoted. I know how tough the Championship is and it won't be any different for us.
"We'll have to work hard for it but the squad is very good and my job will be to help them push for promotion."
Vice-chairman and director of football operations Tony Khan said: "Michael Hector is a talented central defender with experience in the Championship, where he was Sheffield Wednesday's Player of the Year last season, and his imposing height will bring a new dimension to our defence.
"Although Michael can't officially join our first team until January, what's important is he's now a member of Fulham Football Club.
"Michael will help us challenge for promotion and make us better in the second half of the season, at a time when depth, experience and quality will be at a premium in the Championship."