I can't believe this: "Boot Camp only supports Windows 7 or later installation on this platform..."

I had this same problem. It would not work if the ISO file was mounted. unmount the ISO, and then point BCA to the file. It should work.

I have also seen issues when it is on the Desktop or Downloads. Documents seems to consistently work. Most likely it is a Spotlight indexing issue.

Finally got it to work! Here are the steps I took on my MacBook Pro (Retina, 15-inch, Mid 2014):

-Go to this URL: https://www.microsoft.com/en-us/software-download/windows7

-Enter your Windows 10 (yes, Windows 10, not 7) license key. It will say that the product is a Windows 10 license key, and will give you links to download Windows 10 ISOs on the same page.

-Download the Windows 10 64-bit ISO. (I put it in my ~/Documents as Loner T suggested.) Note that the name of the ISO file should be Win10_1511_English_x64.iso, and NOT Win10_English_x64.iso. I initially had downloaded the latter, and that gave me aforementioned problems.

-Run BCA, and it finally accepts the ISO:

Also it should be noted that before even posting on this forum asking for help, I made sure that my Windows 10 ISO was not mounted. (My ISO was actually never mounted after downloading it.)

Thanks Loner T for all the super responsive help! Very much appreciated.

Please remember to backup OS X and Windows. Use separate external drives, if possible.

These instructions do not work with a fresh install (which is what I'd like to do). Following the instructions, I download the ISO for 64-bit Windows 10 from Microsoft, start Boot Camp Assistant, select the ISO and a 16GB USB drive to use as the installer drive, and receive the message:

Your bootable USB drive could not be created

Boot Camp only supports Windows 7 or later installation on this platform. Please use an ISO file for Windows 7 or later installation.

The problem is that Boot Camp Assistant is not recognizing the Windows 10 ISO as being a supported version. My MacBook Pro Retina 15" (Late 2013) is up-to-date.

To reiterate, the supplied instructions do not work:

Use Windows 10 on your Mac with Boot Camp - Apple Support

- go to "Perform a new install of Windows 10"

Reach these instructions:

How to install Windows using Boot Camp - Apple Support

After selecting the ISO and destination disks, you get the above error message.

Have you tried moving the file from 'downloads' to 'documents' as mentioned before? This just solved the problem for me on MBPr, late 2013

Please post the MD5sum of the ISO file. The ISO should not be open or mounted. Downloading the ISO over a wireless connection can cause the ISO to be block corrupted. Since Microsoft does not provide an integrity verification mechanism, you get to find out the hard way.