Harding was born in Oxford. He studied trumpet at Chetham's School of Music and was a member of the National Youth Orchestra at age 13. At age 17, Harding assembled a group of musicians to perform Pierrot Lunaire of Arnold Schoenberg, and sent a tape of the performance to Simon Rattle in Birmingham. After listening to this tape, Rattle hired Harding as an assistant to him at the City of Birmingham Symphony Orchestra for a year, from 1993 to 1994. Harding then attended the University of Cambridge, but after his first year at university, Claudio Abbado named him his assistant with the Berlin Philharmonic Orchestra. Harding first conducted the Berlin Philharmonic at age 21. At the time of his first conducting appearance at The Proms in 1996, he was then the youngest-ever conductor to appear there.