A Sonoma County jury found 44-year-old Michael Augustus not guilty on Friday of two counts of assault with a firearm and exhibiting a weapon.
Augustus was accused of pulling the gun on a fellow diner at a Petaluma restaurant last December after bumping the man and yelling obscenities at him.
Augustus's attorney, Christopher Shea, said his client mistook the man for his former brother-in-law and used a profanity to greet him.
He said his client pulled the gun to defuse an ensuing confrontation.
Augustus was fired by the San Rafael Police department in May. Shea says he will try to get his job back.