Proof of Infidelity in Portugal: What Is Legally Valid in a Divorce?
Updated: 2 days ago
Anyone who reaches this point is past the stage of doubt: the question is no longer «is my partner cheating?» but «what does this change in the divorce?». The answer surprises many people. In Portugal, infidelity no longer decides a divorce — but there are specific situations in which evidence still makes a difference, provided it is obtained legally. In this guide we explain where it counts, which evidence has value and what the report from an infidelity investigation adds. This article is for information and is no substitute for a lawyer's advice.
Quick answer: is proof of infidelity legally valid in a divorce?
In Portugal, since 2008, divorce has not depended on fault: you do not need to prove infidelity to divorce, and it does not in itself determine the division of assets or the custody of children. Evidence is still useful in specific situations: showing the breakdown of the marriage when the other spouse does not consent to the divorce, supporting a claim for compensation, clarifying what happened to joint money and assets, and proving facts relevant to maintenance or to the children. It only has value if obtained legally, and it is always the court that assesses it.
What changed: no-fault divorce
Law no. 61/2008 ended divorce based on the fault of one spouse. Today there are two routes. In divorce by mutual consent, both agree and nobody has to justify anything. In divorce without the consent of one spouse, the person applying must show a ground provided for by law — for example, de facto separation for one consecutive year or other facts showing the definitive breakdown of the marriage. In neither case does the court declare anyone «at fault». We explain what has changed and what still counts in Adultery in Portugal: is it a crime?
Where proof of infidelity can still count
1. To show the definitive breakdown of the marriage
When the other spouse does not accept the divorce and a year of de facto separation has not yet passed, you need to show that the marriage has ended for good. A documented extramarital relationship can be one of the facts presented for that purpose.
2. In a claim for compensation
Fidelity is one of the duties of spouses. The injured spouse can claim compensation for the damage caused by the other, under the general rules of civil liability, in proceedings separate from the divorce. The facts and the damage must be proved, and the outcome depends on each case.
3. In the division of assets: money counts, not the infidelity
The division follows the matrimonial property regime, and infidelity does not change each person's share. What may be relevant is something else: proving that joint money or assets were spent or diverted — trips, rent, gifts, transfers. Here the useful evidence is mainly documentary, and your lawyer will tell you what is worth demonstrating.
4. In maintenance
Child maintenance does not depend on the parents' conduct. Between former spouses, the rule is that each provides for themselves, and maintenance is exceptional and set according to needs and means. There is, however, one point where proof of facts is often decisive: the right to maintenance ends if the person receiving it remarries or starts living in a de facto union. Demonstrating that shared life is one of the most common requests in private investigation.
5. In parental responsibilities
Custody is decided according to the best interests of the child. Having cheated on a spouse does not make anyone a worse parent in the eyes of the law. What is relevant are facts affecting the children's wellbeing and safety: neglect, exposure to risk or failure to comply with the arrangements in place.
Which evidence may have value — and which may not
Evidence that can, in principle, be used
A private detective's report, with a dated description of what was observed in public places.
Photographs and video taken in public places, whose value is assessed by the court.
Witness evidence, including testimony from the person who made the observations.
Documents you have legitimate access to, such as joint account statements, invoices or bookings.
Messages you received or took part in. They should be kept in their original format.
Evidence that may have no value — and cause you problems
Messages obtained by accessing the other person's phone, email or social media. We explain the risks in our guide on how to find out about cheating on WhatsApp.
Recordings of calls or conversations you are not part of. They may be unlawful.
Data from spy apps or GPS trackers. See how to detect a GPS tracker on your car if you suspect that you are the one being watched.
Images taken in private spaces, such as a home or a hotel room.
Evidence obtained in breach of privacy or of communications may be disregarded and may expose the person who gathered it to criminal liability.
What a private detective's report adds
A professional report turns suspicions into dated facts: who, where, when, for how long, with photographs and video of behaviour in public places. It is delivered to you, and it is your lawyer who decides whether and how to use it in the proceedings; the detective can be named as a witness to what was observed. We do not guarantee court outcomes — the value of each piece of evidence is decided by the court. We explain the methods in our guide to infidelity investigation and legal evidence.
Before gathering evidence, speak to your lawyer
It is the advice that saves most time and money. The lawyer tells you what is useful to prove in your case — the breakdown, a de facto union, what happened to certain money — and what changes nothing. Only then does it make sense to define the investigation. We have put together a list of the best family law attorneys in Portugal.
If you have already found something, read the 3 essential steps before you confront.
Mistakes that can cost you dearly
Gathering evidence yourself, by accessing phones, accounts or recordings.
Investigating what is not relevant. Proving infidelity in order to influence the division of assets, for example, rarely serves the purpose.
Confronting before speaking to your lawyer, which leads the other person to change behaviour and protect assets.
Sharing the evidence with family or on social media, which may amount to invasion of privacy or defamation.
How we work in these cases
The work begins with a free and confidential initial assessment, ideally with your lawyer's guidance on what needs to be demonstrated. We present a fixed quote with no hidden costs — learn more about how much a private investigator costs in Portugal. Surveillance is carried out in public places and within the law; to organise the fieldwork we normally need 24 hours' notice. All investigations are coordinated by detective Alexandre Ribeiro, a member of WAD (no. 1687), APDPE (no. 1326), LIDEPPE (member no. 33) and IKD.
Frequently asked questions about proof of infidelity in a divorce
Do I need to prove infidelity to get a divorce in Portugal?
No. Since 2008, divorce in Portugal has not depended on fault. It can be obtained by mutual consent or, without the other spouse's consent, on the basis of facts showing the definitive breakdown of the marriage, such as de facto separation for one consecutive year.
Does infidelity affect the division of assets?
As a rule, no. The division follows the couple's matrimonial property regime. What may be relevant is proof that joint money or assets were spent or diverted for the benefit of third parties, a matter your lawyer should assess.
Does the spouse who cheated lose custody of the children?
No. Parental responsibilities are decided according to the best interests of the child, not the parents' marital conduct. Only facts affecting the children's wellbeing or safety are relevant.
Does infidelity give a right to compensation?
It may. The injured spouse can claim compensation for the damage caused by the other, under the general rules of civil liability and in separate proceedings. The outcome depends on proving the facts and the damage in each case.
Is a private detective's report accepted in court?
It can be submitted in the proceedings by the lawyer, and the detective can be heard as a witness about what was observed. The value of the evidence is always assessed by the court, and depends on its having been gathered legally.
Can I use WhatsApp messages as evidence in a divorce?
It depends on how they were obtained. Messages you received or took part in are different from messages obtained through unauthorised access to the other person's phone, which may have no value and expose you to criminal liability. Speak to your lawyer before using them.
Need evidence for your case?
Talking to us is confidential and involves no commitment. We work throughout the country, including Lisbon, Porto and the Algarve. Call or send a WhatsApp message to +351 936 225 975, 24 hours a day, or learn more about our infidelity investigation service.
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