If you are in an open marriage or ending one, you may wonder how Pennsylvania law views non‑monogamy when a marriage breaks down. Questions about whether an open marriage counts as adultery, whether a spouse can still file on adultery grounds, and how that might affect support or property can be difficult to sort through alone.
At Cooper Family Law, we regularly help clients in Philadelphia and the surrounding counties navigate divorce cases that involve sensitive issues like adultery, fault, and non‑traditional relationship agreements.
This article explains how Pennsylvania generally treats adultery in the context of an open marriage and what that can mean in a divorce. It is general information only, not legal advice for your specific situation.
Fault and No‑Fault Divorce in Pennsylvania
In Pennsylvania, a spouse who wants a divorce can proceed on either fault or no‑fault grounds.
- In a fault divorce, one spouse (the “plaintiff”) alleges that the other spouse (the “defendant”) did something the law recognizes as a ground for divorce.
- In a no‑fault divorce, the focus is on the marriage being irretrievably broken, not on proving misconduct.
Under 23 Pa.C.S. § 3301, the fault grounds in Pennsylvania include:
- Desertion
- Adultery
- Cruel and barbarous treatment
- Bigamy
- Imprisonment
- Indignities
Adultery is on this list, but the statute does not define the term. Pennsylvania courts instead use the traditional definition: voluntary sexual intercourse between a married person and someone who is not their spouse.
How Open Marriages Fit Into the Definition of Adultery
In an open marriage, spouses agree, formally or informally, that each may have romantic or sexual relationships outside the marriage. There is nothing in Pennsylvania law that automatically makes such an agreement illegal; consenting adults have wide latitude to set the terms of their relationship.
Legally, though, extra‑marital sexual relationships in an open marriage still fit the traditional definition of adultery: they involve voluntary sexual intercourse with someone other than your spouse. If either spouse wanted to, they could point to those acts and say, “This is adultery,” even if both previously agreed to an open arrangement.
That tension is where problems arise. Open marriages can function smoothly as long as both spouses continue to agree with the arrangement. Conflict often begins when:
- One spouse changes their mind about being non‑monogamous
- One spouse feels the other broke the agreed‑upon rules (for example, by hiding a relationship or forming a deeper emotional bond)
- One spouse wants out of the marriage and looks for a legal ground to support a fault‑based divorce
On paper, a spouse could file for a fault divorce in Pennsylvania, alleging adultery even in the context of an open marriage. Whether that ground ultimately succeeds is a different question.
Is an Open Marriage Considered Adultery for Fault‑Based Divorce?
From a strictly legal perspective:
- Yes. Any voluntary sexual intercourse with a non‑spouse meets the traditional definition of adultery, even when both spouses agreed to an open marriage.
- But practically, it’s complicated. Fault‑based divorces come with built‑in defenses that can block or weaken a claim of adultery, especially when non‑monogamy was mutual and explicitly agreed to by both spouses.
So while a spouse in an open marriage can file for divorce alleging adultery, the other spouse often has strong defenses if the “adultery” was actually part of a mutually agreed arrangement.
Defenses to Adultery in Pennsylvania
Pennsylvania law recognizes several defenses that can defeat or limit an adultery‑based divorce claim. Some come from old common‑law rules; others are written directly into the statute.
Common‑law defenses (23 Pa.C.S. § 3307(a))
Historically, courts recognized defenses such as:
- Condonation – The plaintiff forgave the defendant for prior acts of adultery.
- Connivance – The plaintiff secretly allowed or encouraged the adultery, or turned a blind eye to it.
- Collusion – The plaintiff helped set up or participated in the adultery.
- Recrimination – The defendant shows that the plaintiff also committed adultery.
- Provocation – The plaintiff provoked the defendant into committing adultery.
These concepts derive from older English law and may sound outdated, but they remain part of Pennsylvania’s divorce framework.
Statutory defenses (23 Pa.C.S. § 3307(b))
The statute also lists specific situations that bar an adultery‑based fault divorce, including where:
- The plaintiff also committed adultery
- The plaintiff continued to have sexual relations with the defendant after learning of the adultery
- The defendant acted as a prostitute for the plaintiff, or the plaintiff acted as the defendant’s pimp
- The plaintiff introduced the defendant into the “lewd company” involved in the adultery
Some of these overlap with the common‑law ideas of collusion and recrimination.
How These Defenses Apply to Open Marriages
In an open‑marriage scenario, a few defenses are especially important.
- Condonation: If one spouse knowingly allowed the other to have sexual relationships outside the marriage as part of an open‑marriage agreement, that looks very much like condonation. The complaining spouse effectively agreed in advance to conduct that meets the legal definition of adultery.
- Recrimination: In many open marriages, both spouses have outside relationships. If the plaintiff has also engaged in extra‑marital intercourse, the defendant can raise recrimination, “you did the same thing,” as a defense to an adultery‑based fault claim.
- Connivance or collusion: If a spouse not only tolerated but actively helped arrange or encourage outside relationships, that can undercut an adultery claim.
Because of these built‑in defenses, courts are often reluctant to grant a divorce on adultery grounds when the “adulterous” conduct was part of a mutually agreed open‑marriage structure.
In practice, that means:
- A spouse in an open marriage can still pursue divorce in Pennsylvania
- But they are more likely to proceed on no‑fault grounds (irretrievable breakdown of the marriage), especially if non‑monogamy was mutual and explicit
Is an Open Marriage Considered Adultery for Support or Property Issues?
Adultery can surface in other parts of a divorce case, such as:
- Requests for alimony, where courts may consider marital misconduct in certain circumstances
- Disputes about equitable distribution when one spouse spent significant marital funds on an extramarital relationship
In an open marriage:
- If both spouses knowingly agreed to outside relationships and benefited from that arrangement, it may be harder for one spouse to argue that the other’s conduct should heavily influence alimony or property decisions.
- Courts tend to focus on economic impact and practical fairness, how money was spent, and how the conduct affected the marital estate, rather than punishing non‑traditional relationships when both spouses participated.
Each case turns on its facts, so how much weight a judge gives open‑marriage conduct in alimony or property decisions will depend on your specific agreement, the level of disclosure, and the financial consequences.
Is an Open Marriage Considered Adultery in Pennsylvania?
Putting it all together:
- Legally, yes. From a definitional standpoint, an open marriage involves conduct that qualifies as adultery, because spouses are having sexual relations with people who are not their spouses.
- As a fault ground, it depends. In a genuinely open marriage where both spouses consented and participated, defenses like condonation and recrimination make it much harder to successfully base a fault divorce solely on adultery.
- Practically, many couples use no‑fault divorce instead. When open‑marriage arrangements break down, spouses often choose a no‑fault path that focuses on the marriage being irretrievably broken rather than litigating who technically committed adultery.
How an Attorney Can Help in Open‑Marriage Divorce Cases
Divorces involving open marriages can raise complicated questions about fault, consent, privacy, and the practical impact of adultery allegations. Even when the legal definition of adultery seems clear, the real questions are whether fault grounds make sense in your situation and how they might affect alimony, equitable distribution, or settlement negotiations. A Philadelphia divorce attorney can help you weigh the pros and cons of fault‑based versus no‑fault divorce and decide how much personal detail to put into the court record.
At Cooper Family Law, our practice focuses on family law matters in Philadelphia and the surrounding counties, and we have experience helping clients address adultery and open‑marriage issues in a way that is both practical and respectful of their privacy.
If you are considering divorce after an open marriage or responding to adultery allegations, Cooper Family Law can help you understand how Pennsylvania law applies and design a strategy aimed at achieving fair, workable outcomes.
