(a) Intervention of right. Upon timely application anyone shall be permitted to intervene in an action: (1) when a statute confers an unconditional right to intervene; or (2) when the applicant claims an interest relating to the property or transaction which is the subject of the action and the person is so situated that the disposition of the action may as a practical matter impair or impede the person’s ability to protect that interest, unless the applicant’s interest is adequately represented by existing parties.
Rule 24.Intervention
Group 4: Parties · Last amended April 28, 2015 · Last verified July 13, 2026
In one sentenceRule 24 lets a person who is not yet a party join a pending lawsuit, either as of right when a statute grants that right or the applicant's interest in the property or transaction at stake could be impaired without it, or with the court's permission when the applicant's claim or defense shares a common question of law or fact with the case.
Full Text of Rule 24
(b) Permissive intervention. Upon timely application, anyone may be permitted to intervene in an action:
(1) When a statute confers a conditional right to intervene; or
(2) When an applicant’s claim or defense and the main action have a question of law or fact in common. When a party to an action relies for ground of claim or defense upon any statute or executive order administered by a federal or state governmental officer or agency or upon any regulation, order, requirements, or agreement issued or made pursuant to the statute or executive order, the officer or agency upon timely application may be permitted to intervene in the action. In exercising its discretion the court shall consider whether the intervention will unduly delay or prejudice the adjudication of the rights of the original parties.
Amendment History
Prior: RPPP Rule 24. Adopted May 5, 1967, effective July 1, 1967; amended, effective April 28, 2015.
Plain-English Summary
Rule 24 gives outsiders two doors into a pending case. The first is intervention of right. A person walks through it when a statute already gives them an unconditional right to join, or when they hold an interest in the property or transaction the lawsuit is about and the existing parties might not protect that interest well enough. The court still checks that the application is timely and that the applicant's interest isn't already covered by someone already in the case.
The second door is permissive intervention, which rests on the court's discretion rather than a guaranteed right. A statute might grant a conditional right to intervene, or the applicant's claim or defense might share a question of law or fact with the main action. Rule 24 also gives a government officer or agency a path in when a party's claim or defense rests on a statute, executive order, or regulation that officer administers. Before letting anyone in on this permissive track, the court weighs whether adding the newcomer will unduly delay the case or prejudice the parties already litigating it.
Getting in requires more than asking. Rule 24(c) requires a motion to intervene, served on every existing party under Rule 5, stating the grounds for intervention and attaching the pleading -- a complaint or answer -- that sets out the claim or defense the applicant wants to raise. Courts measure timeliness against how far the case has already progressed and whether the delay in seeking intervention will hurt the parties already in it.
Frequently Asked Questions
What is the difference between intervention of right and permissive intervention under Rule 24?
Intervention of right applies when a statute grants an unconditional right to intervene, or when the applicant has an interest in the property or transaction at issue that existing parties might not adequately protect. Permissive intervention is discretionary: the court may allow it when a statute grants a conditional right or when the applicant's claim or defense shares a common question of law or fact with the pending action, weighing any resulting delay or prejudice.
How does someone ask to intervene in a Washington lawsuit?
Rule 24(c) requires the applicant to serve a motion to intervene on every party under Rule 5. The motion must state the grounds for intervention and be accompanied by the pleading -- the claim or defense -- the applicant wants to file once allowed in.
Can a court deny intervention because the request came too late?
Yes. Both intervention of right and permissive intervention require a timely application. A court weighing a late request also considers, under the permissive track, whether adding the applicant will unduly delay or prejudice the parties already litigating the case.
Can a government agency intervene in a private lawsuit?
Rule 24(b)(2) lets a federal or state officer or agency seek permissive intervention when a party's claim or defense relies on a statute, executive order, regulation, or agreement that officer or agency administers.
Does an intervenor have to file a proposed pleading with the motion?
Yes. Rule 24(c) requires the motion to intervene to be accompanied by a pleading setting out the claim or defense for which intervention is sought.
Source & verification. Rule text and amendment history are
reproduced verbatim from the Washington Superior Court Civil Rules, adopted by the
Supreme Court of Washington. Last verified July 13, 2026. ·
Official source
Also known as: intervention Washington civil rulesright to intervene in a lawsuitpermissive intervention motionjoining an existing lawsuit as a third partyCR 24 intervention Washington