Title 3. Of the Parties to Civil Actions · Chapter 5. Permissive Joinder · Last amended 1971 · Last verified July 28, 2026
Section 378 answers a basic question before a lawsuit even gets underway: who can sue together? Subdivision (a) gives two paths. Multiple people can join as plaintiffs if their claims grow out of the same transaction, occurrence, or series of occurrences and share a common question of law or fact — several drivers hurt in one crash, for example. They can also join if each one asserts a claim or interest adverse to the defendant in the same property or controversy, even without a shared accident or event tying them together.
Subdivision (b) removes a trap that used to sink joint lawsuits: a plaintiff does not need a stake in every claim raised or every form of relief the complaint seeks. The court can award judgment to one or more plaintiffs according to what each has shown, and let the others go without recovery, all within the same case.
Joining plaintiffs this way saves everyone the cost of separate trials over facts the parties would otherwise have to prove again and again. § 379.5 gives the court power to soften the risk that a joint case grows too unwieldy, ordering separate trials or other relief if joinder starts to prejudice or delay any one party.
No. Subdivision (b) allows judgment for one or more plaintiffs based on their own right to relief, without requiring every plaintiff to have a stake in each cause of action.
Yes. Under subdivision (a)(2), plaintiffs may join if each has a claim or interest adverse to the defendant in the same property or controversy, even without a common transaction.
§ 379.5 lets the court order separate trials or other protective measures once parties are joined under § 378, to prevent embarrassment, delay, or undue expense.
No. § 378 is permissive — it says parties "may join" — so plaintiffs choose whether to bring their claims together or file separately.
Amended by Stats. 1971, Ch. 244.