I cant be sure, as i havent tried it! But i see no reason why not. The rear 'arm' has some flexibility, so as long as its possible to attach it 'outside' the disc brake (which the frame would normally be) then it should work fine.
It shoudn't have any bearing on rear disc brakes as long as your frame has the mounting holes at the top of the frame, there is plenty of adjustment also for the bracket to fit most frames, again your frame must have mounting eyelets next to the mudguard mounts.
Great sturdy rack and a good price.Not sure about the disc brakes though.I bought another one of these racks for a mate and sent him some pics of it fitted to my bike.I could send you them if any help to you if you can find a way to get in touch