The 20-year-old Fosu-Mensah will remain at Craven Cottage for the duration of the 2018/19 campaign.
After his loan deal was confirmed, Fosu-Mensah told fulhamfc.com: "I have a good feeling about the Club. It has a nice history, it's a nice Club.
"Fulham has a lot of good players, and it's good for my development to be here. I spoke to the Manager and he gave me a good feeling.
"I'm happy to be here and I want to keep progressing."
"Timothy is a gifted young defender who excels at multiple positions, and his addition will further reinforce a strong and promising squad that we have assembled to compete in the Premier League. Come on Fulham!"