Ngan Suk-wai, 40, was accused of attacking Anis Andriyani on February 24 last year when the Indonesian maid tried to stop the household's dog from barking by shooing it with a broomstick.
Prosecutors had alleged that Ngan then dragged Anis to the kitchen, slammed her hand onto a chopping board and sliced into the 26-year-old's left ring finger with a knife.
But District Court Judge Gary Lam said there was insufficient evidence to prove the claims, and that the wound went too far round Anis's finger to support her testimony of the attack.
Speaking to reporters outside, Ngan said the verdict proved that "not all employers are bad people," adding that she had been "traumatised" by the trial.
Also Read
The decision comes just days after a Hong Kong woman was convicted of beating and starving her Indonesian maid Erwiana Sulistyaningsih in a case that has shone a spotlight on the plight of the city's 300,000 domestic helpers.
Foreign domestic worker rights activist Eman Villanueva said he was "sad and disappointed" over today's verdict.
And while foreign maids in Hong Kong are guaranteed wages and benefits rare elsewhere in Asia and the Middle East, critics say that Sulistyaningsih's case shows how poorly such rules are enforced.
Mother-of-two Law Wan-tung was on Tuesday convicted of beating and starving the 24-year-old maid to the point where she was hospitalised, in a case that sparked outrage in Indonesia and shocked Hong Kong.
A 2013 survey of more than 3,000 foreign domestic workers in the southern Chinese city found that nearly a fifth said they had experienced physical abuse, and 58 percent that had suffered verbal abuse.