Answered by Mukesh
Usually yes, because a gift card is a way of paying rather than a discount itself, so it often sits happily alongside a sale price or a promotion at the brand's checkout. You get the reduced price and then use the card to cover some or all of what remains.
That said, the final say rests with the brand, and a few run promotions that exclude certain payment types or set their own conditions. The brand's terms are where any such limit would be stated, so a quick check avoids disappointment on a big purchase.
In practice, combining a gift card with a sale is one of the nicer ways to stretch its value, letting the recipient get more for the same card. If a particular promotion will not combine, it is the brand's rule at work, not the card failing, and spending it on another purchase works just as well.