A prenuptial agreement can be contested, not simply during a divorce of the parties, but by the children or parents of a deceased spouse. The party contesting the agreement is usually seeking to have it declared void so that the existing probate or divorce laws will apply. Claims may be made that a spouse did not fully understand the agreement or that one spouse forced the other, physically or mentally do sign the agreement. A challenge of this type is often termed duress. To avoid this sort of challenge, the couple should enter into the agreement well before the wedding. While most jurisdictions do not specify a particular time frame, the more time the couple has to review and consider the provisions of the agreement, the more chance a court would find it voluntary. While an agreement proposed and signed a day or two before the wedding is not per se invalid, it may be a factor, which the court considers in deciding whether to uphold the agreement at a later date.

Other grounds for contesting an agreement may be that some misrepresentations took place which induced one spouse to sign the agreement. One spouse may have made misrepresentations about the agreement itself, perhaps that it was non-binding, only for tax purposes, or temporary. The agreement may also face a serious challenge if all assets were not fully disclosed. Although this is another form of misrepresentation, a challenge of this sort is typically termed fraud. An agreement may well be invalid on this basis if one spouse intentionally misrepresents certain aspects of income or assets.

Another theory used to contest prenuptial agreements is that one spouse lacked capacity. If a party was ill, taking medication, which affected mental capacity, or was intoxicated by alcohol or influenced by other drugs, the agreement may not be valid under the rules of basic contract law.