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Can I Sue My Ex’s Mistress for Damages?

Published: September 16, 2017

Last Updated: March 24, 2026

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Can I Sue My Ex’s Mistress for Damages?

This was an interesting question that an Ontario court grappled with several years ago, in a decision that made some interesting points.

The Ontario Superior Court of Justice was asked to determine the potential legal viability of a wife’s lawsuit against her common-law husband’s mistress, and against the fertility clinic where the mistress was employed, and where the wife had been attending to receive treatments.

What Happened?

The wife and her common-law husband began a relationship around 2006, and moved in together in 2007. In May of that year, they became patients at the Markham Fertility Centre and began to receive fertility treatments.

The woman who eventually became the husband’s mistress was a nurse at the Centre and was the couple’s primary contact there. The couple received treatment between 2007 and 2010. At some point during that period of time the husband and the nurse began to have a sexual affair, that ended in March 2010, shortly after the wife learned that she was pregnant. The husband disclosed his relationship with the nurse to the wife. The wife ended up suffering a miscarriage.

The wife sued the nurse, the Centre, and the Centre’s main doctor. She sought general damages for pain and suffering, breach of contract, intrusion upon seclusion, and breach of privacy. She also sought punitive, aggravated, and exemplary damages.

Specifically, the wife argued that she had experienced:

  • Breach of a duty to care and fiduciary duty;
  • Negligence;
  • Intentional and negligent infliction of mental distress;
  • Harassment;
  • Psychological abuse; and
  • Conspiracy to injure.

Among other things, the wife claimed, against the nurse specifically, that the nurse had:

  • Taken advantage of the trust inherent in a patient-nurse relationship in order to establish an intimate relationship with the wife’s husband, against the interests of the wife, and in favour of her own interests;
  • Breached her professional duty of care towards the wife (as a patient) by having the affair with the wife’s husband.
  • Used the wife’s personal information to invade her privacy and cause her injury;
  • Been part of a “conspiracy to injure” through the secret affair she had with the wife’s husband, which continued throughout the time the wife was receiving fertility treatment;
  • Intentionally inflicted mental distress on the wife.

The defendants (i.e. the nurse and the Centre) filed a motion to strike the entirety of the wife’s pleadings, oh the grounds that it disclosed no reasonable cause of action, and claiming that the wife’s claims “do not exist in law”. They noted that Canadian courts have consistently denied compensation to a spouse for emotional hardship arising from the other spouse’s decision to end the relationship, whether or not there was a third party involved.

The Court’s Decision

In determining whether to strike the wife’s claim, the court had to determine whether it was “plain and obvious” that the pleading disclosed no cause of action.The court ultimately allowed the wife’s claim to proceed, finding that a number of her allegations survived the “plain and obvious” test.

With respect to the claim for mental distress, specifically, the court noted:

While the pleading specifically alleges that the traumatic break-up of her relationship with [the husband] resulted in the deterioration of the [wife’s] mental/ physical condition and ultimate miscarriage, the consequences resulting out of the entirety of acts and events pleaded are sufficiently close in time, and sufficiently tied to the parties involved, to support that element of a reasonable cause of action in the tort of intentional infliction of mental distress.  It is not plain and obvious that the plaintiff cannot succeed at trial on the facts pleaded; a cause of action has been made out.

The court further noted, with respect to the claims of a breach of duty of care, that:

…a professional may be found to be in breach of her duty by engaging in sexual relations with a client’s spouse.  Such a breach may constitute professional negligence because it amounts to an unreasonable exercise in judgement to the detriment of the interest of a client.  Where a medical professional provides services and advice on delicate and personal issues such as fertility, family planning, and conception, it can certainly be argued that a unique standard of care may be imposed.

The court noted that such questions would best be left for a full trial.

Lessons Learned

There is no public record of further proceedings in this matter, and it is unclear how subsequent legal proceeding may have unfolded. However, this case raised intriguing questions about the duty and standard of care owed by fertility clinics and medical professionals, particularly in a broader context of family law.

While the court recognized the defendant’s argument that no Canadian court had permitted a person to claim compensation as a result of their spouse’s extramarital affair, in this case, the additional questions of duty of care and similar may have changed that.

If you have questions about separation, divorce, or related aspects of family law, contact the experienced family lawyers at Gelman & Associates. Our knowledgeable, compassionate, results-oriented, lawyers seek to empower our clients to make informed decisions during the separation process.

We provide each of our clients a handbook on separation and divorce, as well as a number of web-based resources in order to help them navigate the process. Our phone lines are open Monday to Friday from 8 AM to 8 PM. Call us at (844) 736-0200 or contact us online for an initial consultation.

 

Written by Lisa Gelman

Senior Lawyer

Senior Lawyer Lisa Gelman has over 25 years of family law experience and founded Gelman & Associates to provide strategic legal counsel in family law matters concerning divorce, parenting, separation, and more.

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