How can I disable ARC for a single file in a project?

For Xcode 4.3 the easier way might be: Edit/Refactor/Convert to objective-C ARC, then check off the files you don't want to be converted. I find this way the same as using the compiler flag above.

Disable ARC on MULTIPLE files:

1. Select desired files at Target/Build Phases/Compile Sources in Xcode
2. PRESS ENTER
3. Type -fno-objc-arc
4. Press Enter or Done

;)

It is very simple way to make individual file non-arc.

Follow below steps :

Disable ARC on individual file:

1. Select desired files at Target/Build Phases/Compile Sources in Xcode

2. Select .m file which you want make it NON-ARC PRESS ENTER Type -fno-objc-arc

Non ARC file to ARC project flag : -fno-objc-arc

ARC file to non ARC project flag : -fobjc-arc

It is possible to disable ARC for individual files by adding the -fno-objc-arc compiler flag for those files.

You add compiler flags in Targets -> Build Phases -> Compile Sources. You have to double click on the right column of the row under Compiler Flags. You can also add it to multiple files by holding the cmd button to select the files and then pressing enter to bring up the flag edit box. (Note that editing multiple files will overwrite any flags that it may already have.)

I created a sample project that has an example: https://github.com/jaminguy/NoArc

See this answer for more info: Disable Automatic Reference Counting for Some Files