Marital Infidelity Definition: How Being Unfaithful Affects Mental Health

Medically reviewed by Majesty Purvis, LCMHC
Updated October 29th, 2025 by Regain Editorial Team

Key takeaways

  • Marital infidelity can come in various forms, including sexual and emotional affairs.
  • Infidelity can damage trust within a marriage and can affect a person’s mental health.
  • Healing from infidelity may require individual and/or couples therapy.

Typically, infidelity is considered having a sexual relationship outside of a marriage or committed partnership, but depending on the person and a couple’s agreements, the definition of infidelity can vary widely. Infidelity can be sexual, emotional, or digital in nature. If infidelity has occurred in a relationship, it can stir up strong feelings of anger, pain, and distrust. However, attending couples therapy can be helpful for sorting through what happened and potentially repairing the relationship.

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Word of the day: What is the infidelity definition?

The Merriam Webster dictionary defines infidelity as “the act of or fact of having a romantic or sexual relationship with someone other than one’s husband, wife, or partner.” However, in consensual non-monogamy, this strict definition doesn’t always hold. Also, some people may consider small seemingly innocuous acts (such as flirting) infidelity if consent hasn’t been given.

Prevalence of infidelity

According to Vogue magazine, sex research indicates that about 21% of people admitted to cheating at some point in their lives, having had a romantic or sexual relationship with someone other than their committed partner.

What is the definition of infidelity to different people?

Depending on people’s history, needs, culture, religion, and agreements within their partnership or marriage, the definition of infidelity can greatly vary. 

Cheating that involves sexual intimacy

Many people consider cheating to involve sexual behavior within extramarital affairs. This typically involves secretly having a relationship with one or more sexual partners outside of a marriage or committed partnership. While sexual intimacy is a common definition of infidelity, there are other behaviors that are considered by some to be cheating.

Cheating that doesn’t involve sex

What people consider cheating isn’t always having sexual encounters outside of a partnership. Having an emotional affair is also considered extramarital infidelity by some. This is when someone cultivates a deep emotional relationship with a person outside the partnership while emotional intimacy in the partnership suffers. Other things that people consider cheating may include:

  • Watching pornography
  • Flirting
  • Texting someone beyond the realm of friendship
  • Hiding the fact that one is married or is in a partnership.

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What happens when problems with sex and sexual behavior interfere in a relationship?

When one partner has sexual relations outside of a relationship, this behavior can lead to a lack of trust. Having sex with others outside the relationship may also lead the other partner to feel they are no longer desired. 

What is sexual infidelity vs. other kinds of infidelity?

Sexual infidelity is just one kind of cheating. Some people consider emotional involvement with others to be cheating, and it may be even more painful than sexual infidelity to some people. Also, others might consider involvement with other people via digital media to be cheating.

Sexual infidelity

Sexual infidelity typically involves having sexual relations with a person outside of a committed relationship without one’s partner’s knowledge and/or consent. This may involve any type of sexual behavior that a couple has not agreed to outside their relationship.

Emotional infidelity

Emotional infidelity is when someone cultivates a deep emotional attachment with a potential romantic partner outside the relationship, and as a result, emotional intimacy in the relationship often erodes. Both sexual and emotional infidelity can be extremely painful to the partner who is on the receiving end of this behavior.

Online infidelity definition

Online infidelity can include a number of activities, including:

  • Flirting with a person over text
  • Secretly engaging with people using an online dating service
  • Watching pornography
  • Pretending like one is single on social media.  

What happens after your partner has been unfaithful?

When you discover that your partner has been unfaithful, you may experience a variety of emotions, including anger and grief. You might consider whether you want to stay or leave the relationship and whether the two of you should attend couples therapy.

Is it helpful to attend therapy for adultery or marital infidelity?

If you’ve experienced infidelity in your relationship, therapy can be an important part of healing, both for a couple and for individuals. 

Marital and family therapy

Infidelity can be hard on any partnership, and it can especially strain marital relationships. Attending couples or marital and family therapy after emotional and sexual infidelity may make a big difference in a relationship. It may help the partner who has been cheated on process grief and help the couple understand why the infidelity happened and move forward with better communication skills. 

Individual therapy

If your partner has cheated on you, attending individual therapy sessions can also be helpful for processing feelings of grief and anger. A therapist may be able to help you determine whether you want to stay in the relationship or leave. If you want to stay, therapy may provide helpful steps you can take to set boundaries and protect your mental health.

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Have you and your partner experienced infidelity?

Online therapy after infidelity

Both individual and online couples therapy have been proven to be just as effective as in-person therapy. Online therapy allows you flexibility with scheduling, eliminates travel time and transportation hassles, and lets you attend therapy sessions from the comfort of your own home or anywhere with an internet connection.

Takeaway

Infidelity is typically defined as having sexual involvement with someone outside of a committed partnership. In reality, what is considered cheating can vary widely between couples, depending on what their personal ideas and partnership agreements are. The various types of infidelity can include sexual, emotional, and online infidelity. Being cheated on can lead to deep feelings of grief, anger, and distrust. Individual therapy may help you come to terms with your feelings, and couples therapy has the potential to help you and your partner repair the relationship.

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