Yes, you can put an infidelity clause in a prenup, and plenty of couples do. Whether a judge will actually enforce it is a different question, and the answer depends on your state’s approach to fault in divorce and on how carefully the clause is written. Some courts uphold these provisions, some reduce them, and some throw them out as contrary to public policy.
What an Infidelity Clause Actually Does
An infidelity clause attaches a financial consequence to adultery. If one spouse cheats, the clause triggers a predetermined penalty on top of whatever the divorce itself would produce. The penalty might be a lump-sum payment, forfeiture of specific property like the family home or a retirement account, or an adjustment to spousal support so the unfaithful spouse pays more or loses their own right to receive any. The clause can apply to both spouses equally or run in only one direction, which is common when one partner has significantly more wealth and the other wants protection.
These provisions are sometimes called “lifestyle clauses” or “no-cheating clauses.” Lifestyle clauses can also cover other conduct like substance abuse or gambling, but the infidelity version is the one couples ask about most.
Will a Court Actually Enforce It?
There’s no federal law on prenups. Enforceability is a state question, and courts have landed in different places. Two doctrines cause most of the trouble.
No-Fault Divorce Public Policy
Every state now offers some form of no-fault divorce, which lets a couple end their marriage without proving either spouse did anything wrong. About a third of states are exclusively no-fault, meaning fault grounds like adultery aren’t available at all. The rest allow both no-fault and fault-based filings.
In exclusively no-fault states, infidelity clauses face the steepest resistance. Courts in those jurisdictions have held that penalizing a spouse for cheating contradicts the legislature’s decision to remove fault from divorce. A California appellate court struck down an adultery penalty provision on exactly this reasoning, concluding that a contract imposing financial consequences for sexual infidelity conflicts with the public policy behind no-fault divorce. Hawaii’s highest court reached the same result, finding that agreements contingent on a spouse’s misconduct force the family court to evaluate fault in direct conflict with no-fault policy.
In states that still recognize fault-based divorce, courts tend to be more receptive. If a judge is already permitted to consider adultery when dividing property or setting spousal support, the argument that an infidelity clause violates public policy is much weaker. More receptive isn’t the same as guaranteed. Even in these states, a clause can still be rejected as unreasonable or one-sided.
Penalty or Liquidated Damages
Even where public policy isn’t an obstacle, ordinary contract rules apply. American courts draw a sharp line between liquidated damages, which are a reasonable upfront estimate of the harm a breach would cause, and penalties, which are designed to punish. Penalty clauses are unenforceable.
This distinction is where most infidelity clauses run into trouble. The harm from adultery is largely emotional, and putting a reasonable dollar figure on it is genuinely difficult. A $50,000 penalty in a prenup between two people with modest assets looks punitive. The same figure between a couple with $20 million in combined wealth might look proportional. Courts evaluate reasonableness at the time the agreement was signed, not at the time of the breach, so the penalty needs to fit the couple’s financial picture when they drafted it. Couples tend to pick round, dramatic numbers that feel satisfying in the moment and bear no relationship to any real financial harm. When a court sees the amount as punishment rather than compensation, the clause falls apart regardless of what the state thinks about fault.
Drafting a Clause That Has a Chance
If you’re going to include one, the drafting choices matter enormously. A careful, proportional provision has a real shot; a vague or punitive one usually doesn’t.
Define Infidelity Precisely
A clause that says “if either spouse cheats” is asking to be thrown out for vagueness. Courts need an objective standard. The agreement should spell out exactly what conduct triggers the penalty. Physical sexual contact only? Emotional affairs or ongoing romantic communication with someone outside the marriage? A single incident, or a sustained relationship? The more specifically the clause answers these questions, the better it holds up. Negotiating that language is uncomfortable, which is why many couples skip it and end up with something too vague to enforce. The discomfort of drafting the definition is cheap compared to the cost of litigating one that doesn’t have it.
Keep the Penalty Proportional
The financial consequence should bear a rational relationship to the couple’s overall wealth and to the economic disruption an unexpected divorce would actually cause. A modest percentage of marital assets, or an amount that approximates the cost of restarting one’s life, is far more defensible than a number designed to devastate the cheating spouse. Compensation for disruption, not revenge.
Include a Severability Clause
A severability provision says that if a court strikes down the infidelity clause, the rest of the prenup survives. Without it, an unenforceable infidelity clause could theoretically pull the whole agreement down with it. Any competent prenup includes one, but it matters more when the agreement contains a provision this legally uncertain.
Get the Prenup Itself Right
An infidelity clause is only as strong as the agreement containing it. Most states follow some version of the Uniform Premarital Agreement Act or its 2012 successor, the Uniform Premarital and Marital Agreements Act, which together have been adopted in 28 states and the District of Columbia. Under those rules, a prenup can be thrown out for involuntary consent or duress, lack of a reasonable opportunity to consult independent counsel, or inadequate financial disclosure. A court can also refuse to enforce a specific term it finds unconscionable at signing, or one that would cause undue hardship due to a substantial change in circumstances.1Uniform Law Commission. Uniform Premarital and Marital Agreements Act Signing the agreement well in advance of the wedding, rather than in the days before it, reduces the risk that someone later claims they felt pressured.
Proving the Affair
Even a perfectly drafted clause creates a practical problem: someone has to prove the infidelity actually happened. The burden falls on the accusing spouse, and courts generally expect more than suspicion or rumor. Credible evidence looks like text messages, emails, photographs, social media records, witness testimony, or a private investigator’s report. Gathering it is expensive, invasive, and emotionally exhausting.
One of the main selling points of a prenup is that it simplifies divorce by settling financial terms in advance. An infidelity clause can do the opposite. It adds a contested factual question that requires a full evidentiary hearing, and it can turn a relatively straightforward divorce into a protracted courtroom fight over intimate details of the marriage. Some accused spouses agree to the penalty just to avoid the exposure and legal fees of fighting it, which means the clause can function as leverage even when its enforceability is questionable.
What an Infidelity Clause Cannot Reach
Two areas of family law are off-limits to prenups entirely, and no infidelity clause changes that.
Custody is decided on the best interests of the child, not on what the parents agreed to before the child existed. A clause cannot award custody to the non-cheating spouse or restrict the unfaithful spouse’s parenting time. An affair by itself does not make someone a bad parent under the best-interests standard. Adultery becomes relevant to custody only when it directly harmed the child, such as neglect during the affair or exposure to dangerous situations.
Child support belongs to the child, not the parent. A prenup cannot waive, limit, or modify child support obligations, and any attempt to do so is unenforceable. In some states, including such a provision can call the validity of the whole agreement into question. Support is set based on each parent’s income, the child’s needs, and the custody arrangement, not on marital misconduct.
Infidelity Clauses in Postnuptial Agreements
These clauses don’t have to sit in a prenup. They can also appear in a postnuptial agreement, signed after the wedding. In practice, the common scenario is that one spouse gets caught cheating, promises to change, and the couple drafts an agreement imposing consequences if it happens again.
The enforceability challenges are the same, and in some ways worse. Postnups face greater judicial scrutiny because spouses already owe each other fiduciary duties during the marriage, and the emotional context of drafting an agreement after a discovered affair raises obvious questions about duress and voluntariness. The California case that became the leading authority against infidelity clauses actually involved a postnup, not a prenup. If you’re considering this route, both spouses should have independent attorneys, and the agreement should be signed only after emotions have cooled enough for both parties to negotiate freely.
What It Costs
A prenup with an infidelity clause costs more than a standard prenup because the drafting requires greater precision and the enforceability questions may take more attorney time. Each spouse needs their own lawyer, so the cost doubles.
Prenups generally run between $1,500 and $10,000 or more per person, with family law attorneys charging hourly rates from roughly $250 to $1,000 depending on experience and location. A straightforward agreement for a couple with simple finances lands toward the lower end. One with an infidelity clause, detailed definitions of prohibited conduct, carefully calibrated penalties, and a severability provision pushes toward the higher end. For couples with substantial or complex assets, the combined bill can easily exceed $15,000.
The drafting cost is trivial next to the cost of litigating a badly written clause. If the infidelity provision gets contested, each spouse can expect to spend tens of thousands of dollars on the evidentiary hearing alone, on top of the normal costs of divorce. Precise drafting upfront is the single best way to keep the clause out of a courtroom fight later.