The actor will be teaming up with stars including singer Robbie Williams, actor Sir Roger Moore, and model Claudia Schiffer for The Halloween Ball, an invitation-only event with a spooky twist.
The Moulin Rouge! star, who has supported Unicef since 2004, insists the ball will play an important role in raising funds to provide essential supplies for children suffering in the war-torn country.
In an interview with Harper's Bazaar, he says, "As it stands today, there are more than one million child refugees and more than three million children needing urgent help inside Syria; the situation for them is critical. Unicef is working day and night to provide clean water, vaccinations, education, and psychological support to those children.
"Once again, I find myself in absolute admiration hearing about incredibly courageous individuals, putting their lives at risk to help save the lives of children. However, the essential supplies are running low; the Halloween Ball will play a very important role in raising the vital missing funds Unicef needs, and only with that support will Unicef have a good chance of reaching every child."
The star has also taken to Twitter.com to share his excitement over the event, writing, "Looking forward to Unicef U.K. Halloween Ball for Syria's children."
The ball will take place in London location on 31 October (13).