Is once a cheater always a cheater true?  Well, not always. However, according to new research, prior infidelity can triple the chance of cheating with a current partner.

New research tells us that unmarried partners who were unfaithful are three times more likely to cheat in their next committed relationship. In other words, to be serial cheaters.

This research didn’t focus on open relationships or emotional affairs.

The survey of 484 adults (unmarried) asked about their relationship history going back five years. Researchers explored whether participants had cheated on their current or previous significant other (and serial cheating), as well as the same information about their partner.

Almost 45% of the study subjects reported cheating in their previous relationship and 44% in their current relationship. In addition, almost one-third said that they had known that their spouse had been unfaithful in the past. Researchers also reported that both men and women were equally likely to report cheating and being cheated on.

Once a cheater always a cheater: Once burned twice shy?

Those who have been cheated on previously were particularly vigilant for the signs it was happening again. They are four times more likely to suspect their current partner. This is an important fact for relationship therapists to keep in mind. 

But a curious distinction was that the subjects who had cheated were no more likely to be suspicious of their current partner than those who hadn’t. Unless they already had proof.

Dr. Knopp said about his research:

“Our results indicated …a two-to fourfold increase in the likelihood of having a partner engage in infidelity if a person knew about or suspected infidelity from a past relationship partner. These findings suggest that previous engagement in infidelity is an important risk factor predicting engagement in infidelity in a subsequent relationship…. Individuals with previous partners who have engaged in infidelity may be at increased risk for partnering with individuals in later relationships who also engage in infidelity because these individuals may be more likely to contribute to relationship contexts associated with higher risk of infidelity.” 

Is the phrase once a cheater always a cheater true?

I’d like to contrast this piece of research with another more critical study that highlights the importance of any discussion of marital status and infidelity.

Pepper Schwartz and Philip Blumstein studied over 12,000 straight and gay co-habitating couples and compared them to married people. Couples who are long-term co-habitators, they found, are not like couples who have been married for the same length of time.

The research revealed that cohabitating couples were less likely to have each other’s back in times of financial stress and are less likely to be faithful during the relationship. They were also more likely to “better deal” their partner and leave for a more attractive relationship.

Cohabitating men were less liable to stick around during any tough times, according to this research. As a whole, these men tended not to have their partner’s back. The research is not a formal accusation of all cohabitating couples. Just the long-term ones.

Two essential things to insist upon: Trust and commitment

Trust and commitment are two important guiding principles in committed relationships. Unmarried long-term couples and committed long-term couples are two different relationships entirely.

Trust and commitment matter. So does managing inconsolability. These are the Twin-Tasks of Affair Recovery.

If you want to buy into the notion that if people cheat, they always will cheat, you are unlikely to forgive.

Inconsolability blocks a couple’s ability to rebuild trust and for the hurt partner to learn how to trust again. Trust and commitment tend to put the brakes on infidelity.

It’s possible for a couple to heal and move past infidelity but you need to rebuild trust and have a substantial commitment with mutually agreed upon interpersonal boundaries.

That implies that there was some level of trust and loyalty in the first place.

Once a cheater always a cheater: Bottom line

The answer is complex. But when couples have little or no trust or commitment from the get-go, it’s more likely. These couples experience the highest rates of infidelity. But mistakes happen and healing does occur in the vast majority of marriages where affairs have occurred.  Couples Retreats with one therapist and a couple can often launch a couple in a more appropriate direction and prevent the kinds of common mistakes we see in marriages where affairs have happened.


The study was published in the journal Archives of Sexual Behavior (Knopp et al., 2017).

Originally published August 6, 2018

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Daniel Dashnaw

Daniel is a Marriage and Family Therapist and the blog editor. He currently works with couples online and in person. He uses EFT, Gottman Method, Solution-focused and Developmental Models in his approaches. Daniel specializes in working with neurodiverse couples, couples that are recovering from an affair, and couples struggling with conflict avoidant and passive aggressive behavior patterns.

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