Brockovich, 52, was arrested late Friday night in Lake Mead after breath tests showed her blood-alcohol level was more than twice the legal limit of .08, according to the Nevada Department of Wildlife.
A game warden reportedly spotted her struggling with her boat at a marina, and she was taken into police custody.
The mother-of-three had slurred speech and was unsteady on her feet as she tried to dock the boat, authorities said.
Brockovich was taken to jail, and later released after posting $1,000 bail.
The now-famous activist was portrayed by Julia Roberts in a Hollywood movie about her life.
The film centered on Brockovich’s efforts to sue Pacific Gas & Electric (PG&E) for polluting the water supply of a small Southern California town.
Roberts went on to win a Best Actress Oscar for her performance in the 2000 film.
Since the film, Brockovich has become a TV star with her own series, ‘Final Justice’.