For Disney, he played Michael Banks in Mary Poppins, Geordie McNab in The Three Lives of Thomasina, and Rodney in The Gnome-Mobile. Coincidentally, his fellow actress in them all was Karen Dotrice, who had starred alongside him in Mary Poppins.
Garber died on June 13, 1977 at the age of 21 in London from pancreatitis as a result of eating raw meat while on a trip in India. In a later interview on Mary Poppins, Dick Van Dyke, one of his co-stars in the film, said that when they filmed the "I Love to Laugh" scene, he was afraid of going up on the wires and was paid a penny every time he had to do it.
Garber was posthumously named a Disney Legend in 2004, and his younger brother, Fergus, accepted the award on his behalf.On the Mary Poppins 40th Anniversary DVD, Karen Dotrice said she regretted not keeping in touch with Garber before his death.