"After 18 months together, I can confirm that Sam and myself have come to a mutual decision to part ways," he wrote.
"I respect Sam wholeheartedly and cherish our new found friendship. It is important to stress that there is no bitterness or scandal however the distance has been challenging at times. This is a very difficult time for the two of us and to be honest I'm absolutely heartbroken!
"Sammy, I think you are absolutely amazing, beautiful in every way and I wish you all the best in the future. I will be listening to your fantastic radio show and look forward to you killing the ratings in 2017. I want to thank everyone for their love and support over the past 18 months, you have all been amazing! Now get back to your holidays and enjoy time with family and friends! #chinup #timehealsallwounds."
Frost, 27, and Mielczarek, 32, met on the first season of Channel Ten's reality TV show The Bachelorette.