The 28-year-old forward joins the club on a permanent deal from Rangers, signing a two-year deal.
Howat has spent her entire footballing career in Glasgow so far, having represented Rangers, Celtic and Glasgow City since her senior debut for the Blue Belles in 2014.
She brings title-winning pedigree to South London, having won four trophies in her second spell with Rangers, as well as three trophies in her two years at Glasgow City.
Born in Dumfries, Howat has represented Scotland once at senior level, making her debut from the bench against Slovakia in a UEFA Women's Euros qualifying fixture last year.
She has already played under Palace Manager Jo Potter, scoring 39 goals in two seasons under her at Rangers.
Manager Jo Potter said: “I'm delighted to welcome Kirsty to Palace. Having worked with her at Rangers, I know first-hand the quality she possesses. She’s a natural finisher and a great character, and I have no doubt she'll be a huge asset to the team.”
Speaking on her move to Palace, Howat said: “I’m really delighted to be here. It's been quite a whirlwind week, but I'm really excited to get going now!”
Everyone at Palace would like to welcome Kirsty to South London and wish her the very best for her career in red and blue.