Easterbrook "concealed evidence and lied about his wrongdoing" and had physical sexual relationships with three McDonald's employees in the year before his termination, the filing said.
The pictures and videos directly refute Easterbrook's assertions to the board of directors during the time leading up to his dismissal that he'd not been involved with any employee other than the one woman he acknowledged courting.
McDonald's filed a lawsuit on Monday accusing its former CEO Steve Easterbrook of lying about sexual relationships with multiple coworkers during his a year ago working at the fast-food giant.
Mr Easterbrook could not immediately be reached for comment.
The lawsuit came nine months after McDonald's ousted Easterbrook without cause, after determining he had engaged in a non-physical, consensual relationship with an employee that violated the fast food chain's policy. He was also eligible for prorated payment for hitting 2019 performance targets.
In an employee memo on Monday, Kempczinski said McDonald's does not tolerate behavior inconsistent with its values and that Easterbrook's conduct "deviated from our values in different and far more extensive ways" than it had known.
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McDonald's said that, had it been aware of this information, it would not have approved the separation agreement that allowed Easterbrook to receive $700,000 in pay and more than $40m in stock-based benefits.
But this moral posturing over the ex-CEO's indiscretions offers McDonald's a welcome chance to grandstand, distracting from what is reportedly a widespread issue within the company.
In May, an global group of labour unions filed a complaint against McDonald's for what it called systematic sexual harassment at the fast food chain's restaurants around the world.
McDonald's said in Monday's complaint that Easterbrook lied to investigators to cover up sexual relationships with at least three McDonald's employees from 2018 to 2019.
The fast food giant is hoping to recover the $40m (£30.5m) in compensation and severance benefits that Easterbrook received when he was ousted from the company in November following accusations that he was engaged in a relationship with one of his employees.
One day after Mr Easterbrook's departure, McDonald's announced that its top human resources executive, David Fairhurst, who joined McDonald's in 2005 and was named chief people officer at the restaurant chain in 2015, had also left.
McDonald's has taken steps to halt harassment in its ranks. But franchisees - who own 95% of McDonald's US restaurants - aren't required to offer it.