Can I put an AFCI receptacle on a branch circuit that shares a neutral with another branch circuit?
Arc-Fault Circuit Interrupter (AFCI) receptacles are similar to Ground-Fault Circuit Interrupter (GFCI) receptacles, in that they both operate on the Line / Load idea. When connecting an AFCI receptacle, downstream devices are only protected if they are connected to the Load side of the device.  If devices are connected in parallel using pigtails on the Line side, they will not be protected by the AFCI device.

Since connection-wise, AFCI and GFCI receptacles are similar. The answers to these questions can be useful in this situation as well.


How can I add a GFCI breaker on two circuits with a shared neutral without rewiring?
How do I install a GFCI receptacle with two hot wires and common neutral?


Basically, these devices only monitor the wires on the Load side of the device. Which means, anything upstream on the Line side doesn't really matter. Sharing a neutral should not be a problem, as long as it's done properly (e.g. don't share a Load side neutral, only share the Line side neutral before the device).