Harding grew up in Sydney, Australia and attended St Andrew's Cathedral School. In 1993, he began a funk band Compos Mentis with his brother Peter, family friend Mike McCarthy and bass player Sam O'Donnell. In 1998, whilst studying social work at university he auditioned for the children's musical group Hi-5. Harding was accepted and became a core member of the group until November 2007 when he left the group after recovering from a broken back and toes from a motorcycle accident at Eastern Creek Raceway earlier in 2007. Whilst Harding was in Hi-5, they won five ARIA Music Awards and three Logie Awards. In 2015, Harding posted on his own channel on YouTube, where it appears he and his daughter singing a few hits of Hi-5 as L.O.V.E. and Some Kind Of Wonderful. Harding worked as a freelance entertainer and musician and sings with the Sydney-based weddings and functions band Soultraders. And now Harding does acoustic shows around the country. Harding is a family man, married to Natasha, is a father of Arielle (which is the bearer of epilepsy) and Beatrix Joelle.
- Tim was replaced by Stevie Nicholson in November 2007.
- Tim is the second original member that left the group.
- Tim left the group because of a motorcycle accident.
- Tim is the original member where from his line there's least replacement cast.
- In the new version of Hi-5 Australia in 2009, Tim Maddren exercised the same functions as an original member of the same name, since in his Season 13, Maddren attended in a few episodes that Harding was part, but it was less time in the band.