While faith is a very personal choice and each of us have the right to believe what we want to, it can be a difficult and thorny issue when revealing those beliefs to your loved ones. While a spouse may be open to your lack of belief in god, your (or his/her) parents may not be so accepting and you can run some serious risks in damaging your relationship if you do not approach the subject properly.
Before you get into the subject with them you’re going to need to do some research. First it’s important to be able to properly define atheism, as your parents may have heard varying definition from a number of resources. Positions such as “weak atheism” (although I wouldn’t use that term), which refers to someone has no particular beliefs, or “strong atheism” which includes the active belief that no gods exist. Be sure to properly explain both if necessary and clearly define what your own position is. Alternatively it’s important to point out whether you’re agnostic or not, as agnosticism is the belief that there “could” be gods but it’s not something that can be proven or disproven. It’s also important to understand the potential consequences of your actions. Theism and Atheism deal with important beliefs, and much of your family’s life may be based around traditions pre-defined by your faith. Shattering such traditions will be up to you to decide and you’ll need to figure out whether you wish to withdraw from such festivals that punctuate life with our family like Christmas or Easter. You can of course still celebrate these holidays if for nothing else than to spend quality time with your family, but that’ll be a decision that’s left up to you.
Not telling your parents at all could have potential consequences as well. Perhaps going to church and letting them believe that you are in fact faithful and believe in your religion when all of along you’re just keeping up a facade is something that could be damaging emotionally, as you’ll need to constantly act like such things are important to you when they really aren’t. Even if you’re hesitant to tell your parents, make sure you decide on a place and time when it well just be you and them and there are no other distractions. Be sure to help them understand that you still love them and that you appreciate what they’ve done for you. Letting them know that you are not rejecting them but their beliefs. If your parents are particularly religious make sure not to disrespect their own opinions and beliefs. It’s more important to let them know this is about mutual understanding, not defining right and wrong.
Finally, be sure to be confident in your decision. If you have doubts, go and speak to your own religious leaders and see what they have to say. Of course it’s likely that they will try and persuade you to rejoin the faith, but it’s important to listen to them with an open mind and see if what they’re saying makes sense. Don’t argue with them or your parents if they raise objections or become irrational, and don’t turn what should be a discussion into a shouting match. If your parents are upset, give them time to think over what they heard and what it meant to you to come out and let them know about your beliefs.