Wipe down the brick fireplace. With a damp cloth, remove any debris and dirt. If there is soot on the bricks, spend an extra minute removing as much of it as you can; the soot can bleed through the finished paint job. Wait for the bricks to dry before painting.
Prime the brick fireplace. Dab the primer into the mortar joints with a paintbrush. Cover all the bricks with the primer. Let the primer dry.
Paint the brick fireplace with latex paint. Use a paintbrush to apply the latex paint to the fireplace. Try to apply the paint in thin coats. Thin coats will dry more quickly, allowing you to apply a second coat sooner. Apply a second and third coat of latex paint to the fireplace as necessary.