I was just wondering what would happen if someone unkowingly cashed a fake money order? Will the person who trys to cash it be in trouble even if they didn't know?

ScottGem

They could be. Depends on how good the forgery is and whether they can prove they weren't aware it was fake.

You can get in trouble for passing counterfiet money under the same conditions.

Fr_Chuck

If you cash it or deposit it in your bank and it "bounces" they will just take the money back out of your account.

and since it is your ID and name and sometimes fingerprint used to cash it, and you are the one they bank gives the cash to, it is you they will come back to, to get paid back.

This is commom in the money order fraud, someone is going to buy something from you, but sends a money order for too much,
or some company is going to have to deposit payments for them, and keep a small percentage and send them the balance.

You are left oweing the bank thousands.