This is another one of the common team problems. Let me assume that you got to know this from one of your friends in the team. If you have not done anything illegal, unethical, dishonest, or something injurious to anyone, do not worry. Here are a couple of famous quotes very apt to this situation- “Great minds discuss ideas. Average minds discuss events. Small minds discuss people” — Eleanor Roosevelt “Those who talk about others, have lots to hide about themselves“ — Unknown People who have a habit of talking bad about other people behind their backs get noticed in the company. They get a bad reputation pretty soon and people start ignoring them and their words. However, being in this situation, the first thing you can do is to talk to this person in private. Discuss what you overheard and try to resolve the issue one to one. If you are able to sort it out, well and good. However, if you again find him/her doing the same, raise the issue directly with your boss or the HR. The office is a place to work and managers recognize the importance of keeping its sanctity. That person will be in a weaker position in the future, as this type of behavior can affect a lot of things including his/her own appraisal.