What Is California Labor Code §3853: Notice and Joining a Third-Party Suit?

If either the employee or the employer brings an action against such third person, he shall forthwith give to the other a copy of the complaint by personal service or certified mail. Proof of such service shall be filed in such action. If the action is brought by either the employer or employee, the other may, at any time before trial on the facts, join as party plaintiff or shall consolidate his action, if brought independently.

What Is Labor Code §3853?

Labor Code 3853 requires whichever side files against a third party first, the worker or the employer, to notify the other side and let it join or merge into the case.

A work injury can produce two different cases. One is the workers' compensation claim against the employer. The other is a civil case against a third party, meaning someone other than the employer who is responsible for the injury. Labor Code 3853 governs what happens once either side actually files that civil case. The side that sues first must send the other a copy of the complaint and must file proof that it did so.

Labor Code 3850 defines who counts on each side of this rule. "Employee" includes the injured worker and anyone else who gains a claim because of the injury or death, such as a dependent. "Employer" includes the employer's insurance carrier. So when the insurer brings that case on the employer's behalf, Labor Code 3853 still applies the same way.

What must happen first when someone sues the third party?

The side that files first must give the other side a copy of the complaint, by personal service or certified mail, and then file proof of that service.

Labor Code 3853 lists only two ways to give that notice: personal service of the complaint, or certified mail. The statute calls for this "forthwith," meaning promptly, right after the case is filed, not weeks or months later. Proof that notice went out, such as a signed certified mail receipt or a proof of personal service, has to be filed in that same case. This step is what lets the other side learn a case exists at all.

What if the worker and the employer already filed separate cases?

If both sides already filed their own cases against the same third party, Labor Code 3853 requires the two cases to be consolidated before trial.

Sometimes neither side waits to hear from the other. The worker files one civil case, and the employer or its insurer files another, both aimed at the same third party for the same injury. When that happens, Labor Code 3853 does not leave two separate trials standing. It requires the cases to be consolidated, meaning combined into one case, before the court hears the facts at trial. A "party plaintiff" is simply a person or company added to an existing case as one of the parties bringing the claim, rather than starting a new case from scratch.

Does Labor Code 3853 set an exact deadline?

No set number of days appears in the statute. It only says notice must go out forthwith, and that joining or consolidating must happen before trial on the facts.

"Forthwith" is a timing word, not a day count. It is generally read to mean promptly and without unreasonable delay, based on the circumstances. Labor Code 3853 does not say ten days, thirty days, or any other fixed number for sending that notice. The one firm cutoff in the statute covers the other step: joining as a party plaintiff, or asking for the cases to be consolidated, must happen at any time before trial on the facts. Waiting until a trial date is close is risky, so acting as soon as a third-party case is filed is the safer course.

How does Labor Code 3853 connect to the other third-party rules?

Labor Code 3853 is one link in a short chain of sections that together govern a work-injury case against a third party.

Labor Code 3852 comes first. It protects an injured worker's right to sue a third party without losing the workers' compensation claim, and gives the employer or insurer a similar right to act. Labor Code 3854 comes in when the employer sues alone. It lets the employer put evidence of what it paid, or still owes, for the injury in front of the court as part of the damages sought. Labor Code 3853 sits between those two rules. It makes sure that whichever side files a case tells the other, and that the two sides end up in one case rather than two. Labor Code 3856 then decides how any money recovered gets divided once the case is resolved.

What should an injured worker save or ask about?

Keep the complaint you were served with and the proof of service, and ask early whether the employer's insurer already has, or plans to file, its own case.

• The complaint that was filed against the third party, and the date it was served.
• The certified mail receipt or proof of personal service showing when notice went out.
• Any letter or claim file note showing whether the employer's insurer has filed, or intends to file, its own third-party case.
• The name and contact information for the attorney handling the civil case, if one has been filed.

A workers' compensation attorney who also tracks the third-party side of a claim can help confirm that notice went out correctly and that the window to join or consolidate has not closed.

A third-party case can move quickly once either side files it, and Labor Code 3853 only protects a worker or an employer who handles that notice correctly. The firm reviews each potential case individually and does not take every matter. Eman Yazdchi is a Certified Specialist in workers' compensation law, certified by the California Board of Legal Specialization, State Bar of California. For a free consultation about a California work injury that may also involve a third party, call (661) 273-1780 or use the contact form.

For the broader picture of a third-party work injury case, see third-party work injury claims in California. For how this step fits into the full claim timeline, see the workers' compensation claim process.