Andrew Skelton, 43, leaked details of nearly 100,000 supermarket staff after he was accused of dealing legal highs at work, prosecutors said.
He then tried to cover his tracks by using a colleague's details to set up a fake email account.
Skelton, of Water Street, Liverpool, denied three charges of fraud but was found guilty at Bradford Crown Court.
At his trial the jury heard how he abused his position as a senior internal auditor at the firm's Bradford head office.
He sent information about staff salaries, bank details and National Insurance numbers to several newspapers and posted it on data sharing websites, in a data breach which cost the company more than Â£2m to rectify.
David Holderness, from the Crown Prosecution Service, said: "Andrew Skelton's motive appears to have been a personal grievance over a previous incident where he was accused of dealing in legal highs at work.
"The potential loss to his victims and the sheer quantity of potentially compromised data was very significant and could have resulted in employees' identities being stolen.
"The sentence imposed today sends out a very clear message that we will robustly prosecute serious fraudsters such as Skelton who believe they are above the law."
A Morrisons employee who posted staff data on the internet over a grudge has been jailed for eight years.