The pop star has signed up to represent Caudwell Children to mark their 10th anniversary along with Rod Stewart, Elizabeth Hurley and Joan Collins.
Caudwell Children was founded by entrepreneur-turned-philanthropist John Caudwell to provide life-changing equipment, treatment and therapy to sick and disabled children living in the UK.
Commenting on his role, Robbie said: "I have known and admired John Caudwell for a long time, he-s a top man. I hugely respect his enthusiasm and commitment to the charity, Caudwell Children, and it is my pleasure to become a GoodwillAmbassador."
Since being founded in 2000, the organisation - which was originally established to help children living in Robbie-s hometown of Stoke-on-Trent - has donated over £11 million to needy youngsters across Britain and the charity hopes the `Angels` singer`s involvement will help them raise even more funds.
Trudi Beswick, CEO of Caudwell Children, said: "We are absolutely thrilled Robbie has committed to supporting the charity. He is undoubtedly one of the world`s greatest ever performers and has entertained millions of people around the world. We are looking forward to working with him to help promote the important work of the charity."
As well donating his time to help sick children, Robbie - who is also a UNICEF Ambassador - is also considering starting his own family.
The 36-year-old star`s fiancee Ayda Field is constantly asking him when they can have a baby and he is slowly readying himself to agree to her wish.
Speaking of becoming a father, Robbie recently said: "I`m feeling good things. She keeps going on about it and really, really wants one - and I`m coming around to the idea. But it`s slowly, slowly catchy monkey."