Lookman will join the Cottagers on an initial loan deal for a fee of around £2million and has sealed a return to the Premier League following his £22.5m move from Everton to Germany last summer.
Winger Lookman, 22, said: "I'm glad to have it over the line and done now. I'm glad I can be here to help the team.
"After the conversations I had with Scott Parker, I got a great feeling, that's the working relationship I want to have. He's young and hungry and I'm young and hungry as well so it's a good match."
Fulham are braced for a busy few days ahead of the closure of the transfer market on Monday and after starting the season with three successive league defeats.
“Ademola, in his young career, has gained experience in the Premier League and Bundesliga and contributed in England's 2017 Under-20 World Cup win, and we believe that he's a very good addition to our squad! Come on Fulham!"