Is masturbation a mortal sin or a venial sin? The Roman Catholic Church divides sin into two categories: venial and mortal. Venial sin is relatively minor in nature. However, a single mortal sin can determine one's eternal destiny after death. The Church teaches that It causes a person to be separated from God. You ask if masturbation is viewed as a mortal or venial sin. Remember, that for a sin to be mortal, three conditions must together be met. It has to be a very serious and grave matter, which is committed with full knowledge and with deliberate consent. What we are saying is that for it to be mortal sin, it would have to be done deliberately