Can I wire a dimmer switch to a three-way switch?

With the right instructions, you will be able to connect a dimmer switch to a three-way switch. Just be absolutely sure you shut off the power to any electrical circuit with which you'll be working.

Remove the face plate from the electrical box. Pull out the black, red and green wires from your three-way switch. Use a wire nut to connect the green wire from the three-way switch to the dimmer switch ground wire. Connect the red wire from the three-way switch to the red wire on your dimmer switch, and connect the black wire from the three-way switch to the black wire on your dimmer switch.