Is Adultery a Mortal Sin?

Is Adultery a Mortal Sin?

Nowadays, adultery is becoming a usual theme in various movies and TV shows. The sad thing is that people patronize it because they relate to it. It resonates with them. Adultery becomes a trend. However, not all stories end up bad, there are those that ended with a changing heart. Despite that, this comes with a guilt that just doesn’t go away. Perhaps, this needs to be confessed not only to the significant other but also to God. In this blog post, we will discuss one of the most frequently asked questions, Is Adultery a Mortal Sin?


To start off, let’s take a look at what the Catechism has to say.

CCC 2380 “Adultery refers to marital infidelity. When two partners, of whom at least one is married to another party, have sexual relations – even transient ones – they commit adultery. Christ condemns even adultery of mere desire. The sixth commandment and the New Testament forbid adultery absolutely. The prophets denounce the gravity of adultery; they see it as an image of the sin of idolatry.”

CCC 2381 “Adultery is an injustice. He who commits adultery fails in his commitment. He does injury to the sign of the covenant which the marriage bond is, transgresses the rights of the other spouse, and undermines the institution of marriage by breaking the contract on which it is based. He compromises the good of human generation and the welfare of children who need their parents’ stable union.”

The Catholic Church, as emphasized by the statements above, reminds its faithful how grave adultery is.


To answer the question, Is Adultery a Mortal Sin?

It depends.

Let’s first have a quick recap of the two categories of sins.

The Catholic Church categorizes a sin depending on its gravity.

Mortal or venial.

A sin is mortal if the following conditions are met.

  • It must involve grave matter
  • Committed with full knowledge that it is a grave sin
  • Committed with deliberate consent

Let’s use adultery as an example.

If a person had an illicit relationship with another, aware that it is a sin but still committed it, then there is a mortal sin.

To elaborate.

First, adultery is a grave matter as it is against the 6th commandment.

Another one is that person committed it with full knowledge. It means there was a consciousness that it is a sin.

Lastly, committed it with full consent. Despite the fact that there was an awareness of how sinful it was, it was still intentionally carried out.

Note that all conditions must be present. If a sin lacks even just one of these conditions, it will then fall as venial.

But as adultery is a grave offense, those who are guilty must still confess it regardless of whether it’s venial or mortal.


As the world is modernly changing, with lustful acts being normalized, sins such as adultery are becoming prevalent. However, there are those who after realizing that it is a sin, change their heart. Correcting their transgression. Asking for forgiveness.

And as Catholics, we believe in second chances. Adultery is a grave matter, but God is merciful. In the Sacrament of Confession, Christ is waiting for those who sinned, to forgive.

That we may seek Christ’s mercy and forgiveness constantly in the Sacrament of Penance,
Loving Mother, pray for us.

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