Swift, who has mostly remained quiet about her political views, explained that recent events have caused her to speak out.
"In the past, I've been reluctant to publicly voice my political opinions, but due to several events in my life and in the world the past two years, I feel very different about that now," she said.
In the post, Swift went on to say that while she has voted for women in the past, she cannot bring herself to vote for Republican Rep. Marsha Blackburn.
"Her voting record in Congress appalls and terrifies me," Swift said. "I cannot vote for someone who will not be willing to fight for dignity for ALL Americans, no matter their skin color, gender, or who they love."
She went on to list that Blackburn voted against equal pay for women and the Reauthorization of Violence Against Women Act. Swift also said Blackburn believes businesses have the right to refuse service to gay couples and that they should not have a right to marry.
"These are not MY Tennessee values. I will be voting for Phil Bredesen for Senate and Jim Cooper for House of Representatives," she said.
Swift then urged her fans to vote, saying the deadline to register in Tennessee is Oct. 9.
"Please, please educate yourself on candidates running in your state and vote based on who most closely represents your values," she said.
Swift will open the American Music Awards on Tuesday. It's her first AMA performance since 2014.