How to disable duplicate message from imessage on Mac and Messages on iPhone?

I don't think there is anything you can do to prevent this. All alerts get "forked" between the two devices that are registered to use that iMessage account. There currently is no way for either device to tell which is the "active" one to receive messages and alerts on.

You are correct. The only way to stop it, is to turn off iMessage. Your frustration is actually the reason they made iMessage. It was designed so you could be working on your Mac, and if you recieved a text message, you could reply with out having to locate your phone. I understand it can be frustrating because in my expeirence, when I'm away from my desk, anyone with access to my computer can then sit there and enjoy my conversation with out me knowing about it... I have since started logging out of Messages on my Mac when I walk away. then no one can see it, and when I log back in, the messages are synced back up again. Good luck!! Cheers!

You COULD make it so your Mac and your iPhone have different email addresses and accounts associated with iMessage but then they would be treated as seperate devices and not see each other's messages.

Fred

You can also require a password when your Mac is wakened from sleep. That's probably faster than logging out of iMessage. And, if there are people around who would violate your privacy by looking at your messages uninvited, the password will prevent them from looking at other things on your computer like your pictures, email, documents.

Wondering if your iphone was on "Do Not Disturb", if it would not notify you with a sound. Your phone would still have a record of the iMessage notifications, but it may remain silent (other than alarms or phone calls) while you are on your Mac.

That could be the case where you could add a password, but that's kind of a difficult task when my wife wants to use the computer or my boss... It's not a matter of them intentionally snooping, its a matter of having notifications pop up when they're using it. For example, when my wife is using the ipad, she doesnt want to see every text in and out...

That's what multiple user accounts are for on a Mac. Set up an accoun for your wife or who ever and enable Fast User Switching. They then get all their own settings and preferences and your sfuff is kept private. It's actually pretty cool. I've also got the Guest account enabled. I can let someone use my computer on a one off basis without their information being saved.

Yes. It would.