Is there a way to hook headphones to a guitar amp?

generally no, unless your amp has specific outputs for it...

you might be able to rig it to work using cables and converter plugs, If your amp has a speaker extension output, but I seriously don't recommend trying it as I'm pretty sure that only leads to bad things happening...

although Im not really to sure, althout its your amp, ears, and headphones your playing with here, not mine...