The Spurs midfielder has lavished praise on his Belgium international team-mate ahead of his side's meeting with West Brom at the Hawthorns on Sunday
The 19-year-old joined the Baggies on loan in August 2012 and has since racked up 22 first-team appearances for the Midlands club, hitting the back of the net 9 times in the process.
Dembele is adamant Lukaku has what it takes to succeed as a Chelsea player once he returns to the London club from his loan spell at West Brom and has warned Spurs they must pay him special attention at the Hawthorns on Sunday.
“I know Lukaku quite well.” Dembele told the Sunday Mirror. “I’m not surprised he is doing so well at West Brom.
“It’s not so easy to go to a club like Chelsea as a young guy. But everybody in Belgium knows what he’s capable of.
“I’ve seen him in a few games and he’s an unbelievable player – strong, he has everything. He has proved this to everyone.
“It’s not for me to decide what Chelsea need, but I know Lukaku is a very good player and I’m happy he plays for my national team.
“I don’t doubt he has the quality to play for Chelsea. He is a very good player and I’m sure he will succeed there.”
Tottenham, who currently sixth in the table, two points behind fourth placed Arsenal but with two games in hand, failed to strengthen significantly during the transfer window other than the arrival of Lewis Holtby from Schalke, who Dembele admits he knew little about.
“I am very happy we signed Lewis Holtby,” he said. ”But to be honest I don’t know a lot about football,
“I don’t watch too much football at home, I only watch the Premier League.
“So I knew Lewis by name, but I didn’t know him very well as a player. A lot of people told me he’s a very good player and I see this now as well.
“But everybody was impressed with him in the first training session and when he came on against Norwich, everybody saw he is a very good player.”