Montana has a single ground for divorce: the marriage is irretrievably broken. You do not have to prove adultery, cruelty, abandonment, or any other wrongdoing, and your spouse cannot defeat the case by blaming you. This page explains the ground, how it is shown, and the limited places a spouse's conduct still comes up. It is part of our Montana Divorce Guide.
The Only Ground: Irretrievable Breakdown
Montana's statutes call divorce a dissolution of marriage. The chapter that governs it states its own purpose: to make "irretrievable breakdown of the marriage relationship the sole basis for its dissolution" (MCA § 40-4-101(5)). That is what people mean when they call Montana a no-fault state.
The court enters a decree if it finds the residency requirement is met, the marriage is irretrievably broken, and parenting, child support, maintenance, and property have been addressed (MCA § 40-4-104(1)). A finding of irretrievable breakdown "is a determination that there is no reasonable prospect of reconciliation" (MCA § 40-4-107(3)).
Two Ways to Show the Marriage Is Broken
The finding has to be supported by evidence of one of two things (MCA § 40-4-104(1)(b)):
- Separation. The spouses have lived separate and apart for more than 180 days before the proceeding began.
- Serious marital discord. There is serious marital discord that adversely affects the attitude of one or both spouses toward the marriage.
The word between them is "or." A couple who still share a home can proceed on serious marital discord, and a couple who have been apart for more than 180 days can rely on that alone. Our page on whether you have to be separated first covers this in more detail.
What the Petition Has to Say
The petition must be verified, and it must allege that the marriage is irretrievably broken on one of those two bases. When the basis is serious marital discord, the statute adds that the petition states "there is no reasonable prospect of reconciliation" (MCA § 40-4-105(1)(c)).
The statute does not ask for a narrative of what went wrong. It asks for the legal basis.
Fault Defenses Are Abolished
Under older divorce law, a spouse could resist a divorce by raising defenses, for example that the filing spouse had forgiven the misconduct or had behaved just as badly. Montana ended that. MCA § 40-4-105(4) provides that previously existing defenses to divorce and legal separation, "including but not limited to condonation, connivance, collusion, recrimination, insanity, and lapse of time, are abolished."
A spouse can still deny under oath that the marriage is irretrievably broken. In that case the court considers all relevant factors, including the circumstances that led to the filing and the prospect of reconciliation, and either makes the finding or continues the matter for a further hearing (MCA § 40-4-107(2)). See whether your spouse can refuse a divorce.
Where a Spouse's Conduct Does and Does Not Matter
No-fault applies to more than the ground. Several of the statutes that decide the financial issues say so in the same words.
| Issue | Role of conduct | MCA |
|---|---|---|
| Ending the marriage | Not considered. The only question is whether the marriage is irretrievably broken. | §§ 40-4-101(5), 40-4-104(1)(b) |
| Dividing property | Divided "without regard to marital misconduct." The court does consider the contribution or dissipation of value of the spouses' estates. | § 40-4-202(1) |
| Maintenance | Amount and duration are set "without regard to marital misconduct." | § 40-4-203(2) |
| Child support | Set "without regard to marital misconduct." | § 40-4-204(1) |
| Parenting plan | Decided by the best interest of the child. The listed factors include physical abuse or threat of physical abuse and chemical dependency or chemical abuse. | § 40-4-212(1) |
Two rows deserve a closer look. First, "marital misconduct" is different from what a spouse did with the property. The property statute tells the court to consider the contribution or dissipation of value of the spouses' estates (MCA § 40-4-202(1)), so wasting or destroying assets is a financial question the court can weigh. See how property is divided.
Second, parenting is decided by the child's best interest, not by which spouse was the better partner. The factors a court considers include physical abuse or threat of physical abuse by one parent against the other parent or the child, and chemical dependency or chemical abuse by either parent (MCA § 40-4-212(1)(f), (g)). Conduct matters there because of its effect on a child. See the best interest factors.
If There Has Been Abuse
No-fault does not mean a court ignores safety. Abuse is relevant to parenting, to temporary orders that can exclude a spouse from the home (MCA § 40-4-121(2)), and to orders of protection, which are a separate proceeding. If you are in danger, call 911. The National Domestic Violence Hotline is 1-800-799-7233. Our Montana Domestic Violence Guide explains orders of protection, and divorce and domestic violence covers how the two cases interact.
What No-Fault Means in Practice
Because the ground is not about blame, the evidence in a Montana dissolution is mostly about the four issues the decree settles: parenting, child support, maintenance, and property. Time spent proving who was at fault for the breakup does not move the property division or maintenance, because the statutes take misconduct off the table for both.
That is one reason many spouses are able to settle. The legislature listed promoting "the amicable settlement of disputes" among the chapter's purposes (MCA § 40-4-101(2)). If you and your spouse want to work out terms together, our Cooperative Family Law page describes one way to do that.
This page explains Montana law in general as of the 2025 Montana Code Annotated. It is not legal advice about your specific situation.