Steve Girling, 36, from Norfolk has been jailed for four years after stealing £1 million from his former employer, Premier Education Group, to feed a gambling habit which he says almost cost him his life.
Norwich Crown Court was told he diverted company money into his own account and then tried to cover his tracks by adjusting spreadsheet entries.
He admitted a single count of theft at an earlier hearing.
Judge Stephen Holt, sentencing, told Girling: "For nearly a four-year period you stole over a million pounds from the company you worked for as finance director.
"These thefts were skilfully planned and executed so the loss to the company wasn't noticed and was passed by three separate audits."
- Click to watch a report from Norwich Crown Court by ITV News Anglia's Kate Prout
Before the sentence, Girling told ITV News: "I was playing £100 a spin and spinning every few seconds.
"Some days I'd do five figures on the slots. I was playing as soon as I woke up in the morning - any spare time.
"I was neglecting everything really, friends and family.
"I had suicidal thoughts. I'd self-harmed and overdosed. The pain was awful and there were times when I thought it was better that I wasn't here."
Girling, of Folgate Close in Costessey near Norwich, admitted stealing from his employer Premier Education Group between May 2014 and October 2017.
Judge Steven Holt said Girling spent £500,000 of the stolen money on gambling "but the other half is effectively unaccounted for".
He said Girling had put money into his personal savings account, set up Isas for his children, moved to a larger house, paid off that mortgage "and possibly another mortgage".
As Steve Girling blew thousands of pounds a night, betting firms sent him rewards.
He was classed as a VIP customer and treated him - along with his wife and friends - to lavish horse racing trips.
Girling says he has not bet since.
He is now training as a life coach and working with charities to try to help other problem gamblers.
For help and advice on gambling addiction