Is thinking about sex a sin?

Is Thinking about Sex a Sin?

Have you ever caught yourself thinking about sex? If so, what was your reaction? Did you feel pleasure? Or did you feel guilt? I know the question is extremely awkward. But, in this blog post, I’d like to raise awareness of the danger of sexual thoughts to a soul.


The Catechism of the Catholic Church states

CCC 2351  “Lust is disordered desire for or inordinate enjoyment of sexual pleasure. Sexual pleasure is morally disordered when sought for itself, isolated from its procreative and unitive purposes.”

This sexual pleasure can be in a form of thought that can lead to a sin such as masturbation.

CCC 2352 “By masturbation is to be understood the deliberate stimulation of the genital organs in order to derive sexual pleasure. Both the Magisterium of the Church, in the course of a constant tradition, and the moral sense of the faithful have been in no doubt and have firmly maintained that masturbation is an intrinsically and gravely disordered action. The deliberate use of the sexual faculty, for whatever reason, outside of marriage is essentially contrary to its purpose. For here sexual pleasure is sought outside of the sexual relationship which is demanded by the moral order and in which the total meaning of mutual self-giving and human procreation in the context of true love is achieved.”

Aside from masturbation, sexual thoughts can also turn into other grave lustful sins such as fornication and adultery.

And this makes sexual thoughts perilous.

Sexual Thoughts

With lust being normalized nowadays, people seem to rationalize many sexual sins. Pornography, masturbation, fornication, and adultery are prevalent. That if you don’t practice them you are outdated. Vulgarity is not vulgar anymore. Chastity is downplayed.

That’s why it is not that surprising to know that there are people who are having sexual pleasures even in their thoughts.

That’s how corrupt lust can be!

Now, let’s analyze sexual thoughts as a sin.

Is thinking about sex a sin?

Thinking about sex can be a sin or not at all. It depends on the person’s intention. If one deliberately thinks of sex to have pleasure, there can be sin. If on the other hand, sexual thoughts just abruptly come to mind out of nowhere and reject them, then there is no sin. The intention suggests whether it is a sin or not.

Intrusive Thoughts

As mentioned above, having sexual thoughts can be intentional or not.

If it is not deliberately thought of and just suddenly entered your mind, they are intrusive thoughts. These are unwanted thoughts that unexpectedly enter one’s head. These are usually disturbing and impure.

Having these is common for those with religious Obsessive-Compulsive Disorder or Scrupulosity. But, note that the moment they get into their minds does not mean they sin because there is actually no intention in the first place.

To know more about scrupulosity, you might want to check this.

Biblical Reference

Here are some of the bible passages that relate to sexual thoughts.

“But I say to you, everyone who looks at a woman with lust has already committed adultery with her in his heart.”

Matthew 5:28

“For from the heart come evil thoughts, murder, adultery, unchastity, theft, false witness, blasphemy.”

Matthew 15:19

The verses above just prove how sexual thoughts are sinful.

Mortal vs Venial Sin

Now that we know that having sexual thoughts can be a sin, let’s proceed to tackle what category it would fall.

Is having sexual thoughts a mortal or venial sin?

Just a quick recap, the Catholic Church categorizes sin depending on gravity.

It could be mortal or venial.

These are the conditions for a sin to be mortal.

  • It must involve grave matter
  • Committed with full knowledge
  • Committed with deliberate consent

Let’s use one of the lustful sins as an example, sexual thoughts.

If one had sexual thoughts for pleasure, aware that it is a sin but still committed it, then there is a mortal sin.

To elaborate.

First, having sexual thoughts for pleasure is lust and lust is a grave matter.

Next, that person committed it in full knowledge. Meaning there was an awareness that it is a sin.

Lastly, committed it with full consent. In spite of the fact that there was an awareness that it was sinful, it was still deliberately committed.

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


Since lust is a grave matter. This sin must be confessed.

A sexual act is probably one of the most embarrassing sins to confess. It can be awkward.

To help you with that, here’s a quick guide to confessing sexual sins such as sexual thoughts. It will walk you through what to say to the priest during confession to make the flow smooth.

If you are struggling with scrupulosity, you check this Confession Guide.

Or if it is your first time on confession, here is a guide for beginners.


Having sexual thoughts could also be a result of pornography. If you have an addiction to adult content or maybe recovering from it, here are some of the best resources available.

Some Parishes also have Office for Family Life. You can ask yours for you to get a counselor. Or you can also open your struggles to your Spiritual Director if you have one.


We Catholics, are called to be pure. It is our duty to guard our thoughts against the possibility of sins such as lust.

People easily fall for this sin. The temptation can be too enticing not to nibble. If you fall, the Sacrament of Penance will wash away your sins. It can grant you the absolution your soul needs. But note that true repentance happens when we change for the better. Avoiding the impurity and living a chaste life.

Although it is not easy all the time, staying away from lust is very much possible.

Through prayer, Sacraments, and the resources above, one can live a life of purity.

May we always call on our Blessed Mother in times of temptation.

Loving Mother, pray for us.

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