A person who is not a party to an appeal may file in the court of appeals a petition to intervene in the appeal. A party may file a response to the petition within 11 days after service of the petition. The court may grant the petition upon a showing that the petitioner’s interest meets the requirements of s. 803.09 (1), (2), or (2m).
809.13.Rule (Intervention).
Ch. 809: Rules of Appellate Procedure · Last amended 2017 · Last verified July 15, 2026
In one sentenceSection 809.13 lets someone who is not already a party to a pending appeal file a petition to intervene, gives the existing parties 11 days to respond, and allows the court of appeals to grant intervention if the petitioner’s interest satisfies the standards in section 803.09(1), (2), or (2m).
Full Text of Section 809.13
Official Notes
Judicial Council Committee’s Note, 1978: Former s. 817.12 (6) permitted the addition of parties but did not set the criteria for doing so. This void is filled by making the intervention rule in the Rules of Civil Procedure applicable to proceedings in the Court of Appeals. [Re Order effective July 1, 1978]
Judicial Council Note, 2001: The 7-day time limit has been changed to 11 days. Please see the comment to s. 808.07 (6) concerning time limits. [Re Order No. 00-02 effective July 1, 2001]
Plain-English Summary
Section 809.13 gives a nonparty a way into an appeal that is already underway. That person files a petition to intervene in the court of appeals, and any existing party can respond within 11 days of being served with the petition.
The standard for granting intervention is not a separate appellate-specific test. Instead, section 809.13 borrows the intervention requirements already used in circuit court, requiring the petitioner to show that its interest meets one of the standards in section 803.09(1), (2), or (2m), the same framework that governs intervention as of right or by permission at the trial level. Applying that familiar standard on appeal keeps the analysis of who can intervene consistent whether the case is still in circuit court or already on review.
Frequently Asked Questions
Can someone who was not a party at trial join an appeal that is already pending?
Yes. Section 809.13 lets a person who is not a party to an appeal file a petition to intervene in the court of appeals.
How long do the existing parties have to respond to a petition to intervene?
A party may file a response to the petition within 11 days after service of the petition.
What standard does the court of appeals use to decide whether to allow intervention?
The court may grant the petition upon a showing that the petitioner’s interest meets the requirements of section 803.09(1), (2), or (2m).
Is the intervention standard on appeal different from the one used in circuit court?
No. Section 809.13 applies the same intervention standard set out in section 803.09, the civil procedure rule governing intervention at the trial level.
Who decides whether to grant a petition to intervene in a Wisconsin appeal?
The court, meaning the court of appeals or, if the proceeding is in the supreme court, the supreme court.
Amendment History
History: Sup. Ct. Order, 83 Wis. 2d xiii (1978); 1981 c. 390 s. 252; Sup. Ct. Order No. 00-02, 2001 WI 39, 242 Wis. 2d xxvii; 2017 a. 369.
Source & verification. Section text and official notes are
reproduced verbatim from the Wisconsin Statutes, published by the
Wisconsin Legislature (Legislative Reference Bureau). Last verified July 15, 2026.
· Official source
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