Video report by ITV News Sports Reporter Amy Lewis
The Spurs striker made his senior debut during a loan spell at Orient in 2011 and was brought up close to the club's ground.
Kane's decision to pay for the front-of-shirt sponsorship for Orient's three kits has received approval from the Premier League, English Football League and Football Association.
The sponsorship will be donated to three causes, with the home shirt donning a thank you message to the frontline heroes of the coronavirus pandemic, the away shirt showing Haven House Children's Hospice's logo and the third kit donated to mental health charity Mind.
Kane, who scored five goals in 18 games for Orient, said: "I was born and brought up only at a couple of miles from the stadium and I am really happy to have the opportunity to give back to the club that gave me my first professional start.
"This also gives me a platform to be able to say a big thank you to the many frontline heroes and charities out there who provide care and support during these challenging times."
Orient chief executive Danny Macklin added: "When we discussed with the England captain Harry Kane and his team at CK66, we all decided that we wanted this to be unique.
"We wanted to say thank you for the exceptional hard work and dedication of the frontline heroes during this pandemic and also bring attention to the other charities out there who have all suffering financial loss due to the pandemic.
"Thank you, Harry, for your amazing support and generosity - you are a true role model for the modern game."
Orient will give 10 per cent of all shirt sales back to Kane's nominated charities.