In 1993, Erin Brockovich is an unemployed single mother of three children who has recently been injured in a traffic accident with a doctor and is suing him. Her lawyer, Ed Masry, expects to win, but Erin's confrontational courtroom behavior under cross-examination loses her the case, and Ed will not return her phone calls afterwards. One day, he arrives at work to find her in the office, apparently working. She says that he told her things would work out and they did not, and that she needed a job. She asks Ed for a job, which he reluctantly gives her.
Erin is given files for a real estate case where the Pacific Gas and Electric Company (PG&E) is offering to purchase the home of Donna Jensen, a resident of Hinkley, California. Erin is surprised to see medical records in a real estate file and visits Donna, who explains that she had simply kept all her PG&E correspondence together. Donna appreciates PG&E's help: she has had several tumors and her husband has Hodgkin's lymphoma, but PG&E has always provided a doctor at their own expense. Erin asks why they would do that, and Donna replies, "because of the chromium". Erin begins digging into the case and finds evidence that the groundwater in Hinkley is seriously contaminated with carcinogenic hexavalent chromium, while PG&E has been telling Hinkley residents that they use a safer form of chromium. After several days away from the office investigating, she finds her possessions missing from her desk. She is then informed by Brenda, Mr. Masry's secretary, that she has been fired for missing a week of work. Despite protesting that she has been out conducting research, Erin nevertheless leaves defeated.
Later, Ed visits Erin because he needs the documents she found while investigating, and she takes the chance to request her job back in return. Rehired, she continues her research, and over time, visits many Hinkley residents and gains their trust. Ed and Erin hold a barbecue in order to speak to many of the residents and explain to them what PG&E has been trying to get away with, at which point Erin is awkwardly flirted with by one of the men. Erin and Ed find numerous medical problems in Hinkley, and that virtually everyone has been treated by PG&E's doctors who have led them to believe their issues are unrelated to the "safe" chromium. The Jensens' claim for compensation ultimately becomes a major class action lawsuit. Unfortunately, Ed explains that all direct evidence is linked solely to PG&E Hinkley, rather than PG&E corporate. Until headquarters can be implicated, PG&E corporate can deny any knowledge of what's happening in Hinkley.
Knowing that PG&E could slow any settlement for years through delays and appeals, Ed decides to pursue binding arbitration rather than a trial by jury, but PG&E will only agree to arbitration if 90% of the plaintiffs agree. During a town hall meeting with the Hinkley residents, Ed goes over the plan with everyone feeling unsure. At one point, Erin spots the man who flirted with her at the barbecue. She brushes off the man's looks, as Ed struggles to explain the virtue of arbitration versus a 10–15 year battle in court. Eventually everyone in attendance agrees, and over the next several days Ed and Erin persuade all 634 plaintiffs to go along.
One night Erin stops at a bar to see one of the residents, when she unexpectedly bumps into the man she's seen at the last two Hinkley events. After some uncomfortable conversation the man reveals himself to be named Charles Embry; a former PG&E employee who "destroyed documents." Erin realizes Charles has been trying to communicate with her, and is finally able to listen to his story. Charles tells Erin he and his cousin were both employees with PG&E Hinkley. Heartbroken, he tells her his cousin has just died; dying painfully from the poison he interacted with at PG&E. He goes on to explain that PG&E tasked him with destroying documents, but, "as it turns out, [he] wasn't a very good employee".
Embry gives Erin the documents, including a 1966 memo proving corporate headquarters knew the water was contaminated with hexavalent chromium, and advised PG&E Hinkley to keep this secret. The judge orders PG&E to pay a settlement amount of $333 million to be distributed among the plaintiffs, $5 million of which goes to the Jensens. Erin brings her boyfriend with her when she tells them about it, and he is happy when he understands what it was all for.
In the aftermath, Ed hands Erin her bonus payment for the case, but warns her he has changed the amount. She begins complaining loudly that she deserves more respect, but is astonished to find that he has increased it—to $2 million.
Julia Roberts as Erin Brockovich
Albert Finney as Edward L. Masry
Aaron Eckhart as George, Erin's biker boyfriend
Marg Helgenberger as Donna Jensen
Tracey Walter as Charles Embry
Peter Coyote as Kurt Potter
Cherry Jones as Pamela Duncan
Scarlett Pomers as Shanna Jensen
Conchata Ferrell as Brenda, Mr. Masry's secretary
Erin Brockovich as Waitress Julia
Michael Harney as Pete Jensen
Veanne Cox as Theresa Dallavale
Scotty Leavenworth as Matthew Brown
Gemmenne de la Peña as Katie Brown
Gina Gallego as Ms. Sanchez, a PG & E attorney
T. J. Thyne as David Foil
Valente Rodriguez as Donald
Jamie Harrold as Scott
Edward L. Masry as Diner Patron (uncredited)
Manning Bailey as Party Extra (uncredited)
a dramatization of the true story of Erin Brockovich who fought against the energy corporation Pacific Gas and Electric Company (PG&E) regarding its culpability for the Hinkley groundwater contamination incident. The film was a box-office success, and gained a positive critical reaction.