"Congrats," Palin wrote in an Instagram post. "Climb upon Geraldine Ferraro's and my shoulders, and from the most amazing view in your life consider lessons we learned."
A former Alaska governor, Palin was John McCain's running mate in 2008. Democrat Ferraro ran with Walter Mondale in 1984. Harris is the first Black woman to run for vice president on a major-party ticket.
Palin's post included a series of tips for Harris, including "trust no one new," "fight mightily to keep your own team with you," "don't get muzzled" and "don't forget the women who came before you."
She also warned Harris that "yahoos running campaigns will suffocate you with their own self-centered agenda" and urged Harris to "stay connected with America as you smile and ignore deceptive 'handlers' trying to change you."
McCain and Palin were defeated in 2008 by Barack Obama and his running mate, Biden.