Christopher Rawding had been employed by the company as a cash collector obtaining large payments from customers before being trusted as an accounting representative.
Newcastle Crown Court heard that Rawding's offending took place roughly between April 2015 and October 2018, when he used the money to fund his gambling addiction.
Prosecutor Barry Robson said that the offending came to light when credit notes were discovered to have been incorrectly applied and missing payments from Nike client Urban Industries were noticed.
Mr Robson added: "At that stage Urban Industries had been contacted.
National Mackem Day 2022: 14 things you'll only understand if you're from Sunderland
Sunderland drunk staggered into traffic after being found slumped at side of road
Met Office announces yellow weather warning for thunderstorms across North East following heatwave
Durham police appeal for help to find 33-year-old in connection with alleged burglaries
Campaigners rally against Local Plan after farmland in Cleadon earmarked for 156 homes
"They were able to confirm that the defendant had emailed them in April 2015 to say there had been a problem with their direct debit to Nike.
"To resolve this the defendant changed it to a different account number. This Halifax bank account was later found to be the defendant's own personal account."
The court heard Rawding, now 36, oversaw bank transfers made to his own account but his offending temporarily stopped midway through 2018 when he was moved to the Netherlands.
In total, Urban Industries had paid £871,476.68 into the Halifax bank account.
Mr Robson added: "The defendant attempted to cover up the fraud but on the 20th of November 2018 an email was received by Nike by the defendant accepting his criminality and tending his resignation."
It was later discovered Rawding had also taken money from another client, Cooshti Ltd, in the same way he had done from Urban Industries.
The amount transferred from Cooshti was £19,315.14, making the total amount of money stolen £890,791.83.
The police became involved upon the discovery of the offending and in interview he admitted he used the money for gambling purposes, and was at times spending up to £5,000 a day on his habit.
Rawding, of Belsay Gardens in Sunderland, pleaded guilty to two counts of fraud by false representation at the magistrates court back in 2019.
Penny Hall, mitigating, said that the defendant fell into gambling addiction upon the death of his grandfather some 12 to 13 years ago before this spiked again when his children were born so he could provide for them.
It was also heard that the gambling companies Rawding used would often return losses to him and treated him like a VIP customer, essentially encouraging him to spend more money, but noted that betting regulations have since changed.
Ms Hall added: "He has been unwell for the majority of the last year. That is having contracted Covid then still having long Covid and then being diagnosed with COPD.
"Prior to him being unwell with Covid, in the first wave of the pandemic he volunteered to help.
"He did a lot of volunteering work to the extent he worked over 800 hours on a voluntary basis."
However, Mr Recorder Lumley sentenced Rawding to 40 months imprisonment.
The judge told him: "You were a trusted employee rising through the ranks in a position of significant trust at Nike.
"It turns out you gambled it all away - £5,000 a day or something like that.
"You are an otherwise good man, a good father and have risen to that position of responsibility with Nike.