Someone said gambling is sinful but i had never heard anything about this before. Is it true?
The Catholic Church teaches that gambling or any form of game of chance isn’t sinful in itself:
“Games of chance (card games, etc.) or wagers are not in themselves contrary to justice. They become morally unacceptable when they deprive someone of what is necessary to provide for his needs and those of others. The passion for gambling risks becoming an enslavement. Unfair wagers and cheating at games constitute grave matter, unless the damage inflicted is so slight that the one who suffers it cannot reasonably consider it significant.”CCC 2413
Gambling can be a form of entertainment but as with all forms of entertainment, overdoing it can become a problem.
It becomes sinful when the gambler pays too much for such entertainment. For instance, in cases of people paying thousands or losing millions while their families and people under their care are suffering are definitely committing sin. It is so too when a person spends so much on other forms of entertainment when their families are in need. So it is about financial morality and this is a serious thing.
It also becomes a sin if an attachment to gambling is formed to the point of preventing one from contributing meaningfully to their family and immediate society. In such case, the person needs to seek psychological help.