Tammy Hands, 49, and David Bondy, 46, were arrested in 2010 after police in Tecumseh alleged that Hands had sex with her doctor, who was married, and recorded it on her smartphone without his knowledge.
The two were accused of trying to blackmail the physician for $25,000, but a judge on Monday acquitted the pair on the extortion charges, as well as a separate charge of voyeurism filed against Hands.
The judge found the doctor's testimony inconsistent and unreliable.
Defence lawyer Laura Joy says Hands and Bondy feel "vindicated" by the ruling.
She says the pair's private lives were "exposed" as the case went on for several years.